Hey
@MikeIke. You probably don't really know me, since I've never ventured much into the FFA. Joe linked me to this thread, though, and I wanted to come by and offer my perspective, too.
When I was 13 and my brother was 15, my mom used to get her nails professionally done. Mostly because my mom is a hyper-sociable person, and professional nail appointments are professional chat appointments. (You gotta do something while the lacquer dries, right?) Her favorite nail tech at the time, we'll call her "Sharon", was around 26 and had a 12-year-old daughter, we'll call her "Mary". Sharon kept telling my mom about how she just couldn't handle Mary, she was doing the best she could but she was a single mother who had dropped out of high school, she didn't have any money, she didn't have any career prospects, she didn't have any parental role models, and she just didn't know what to do.
So my mom and dad-- amazing, awe-inspiring people that they are-- took in Mary and raised her as their own. It was really weird, and hard. That part about how your kids would probably wind up fooling around with Padme? Well, my brother and Mary had already had several hot-and-heavy makeout sessions (they didn't realize she was going to become our "sister" at the time), and I had a huge crush on her for like the first year she lived with us. (I was 13. She was hot.) Eventually, things got to the point where the very thought of fooling around with Mary became super-weird. And I was really, really, really glad by that point that I *hadn't* fooled around with her. Because suuuuuuuuuuper-weird. But had there been an opportunity before we reached that point, oh hell yeah, it'd have happened. Throwing a pair of non-
Westermarcked mixed-gender kids in the middle of puberty together under the same roof is dangerous. Take precautions.
The early going with Mary living with us was really rough. I'm not going to compare it to what you're going through, but she rebelled early and hard. She'd basically been raising herself for a few years and she chafed at any restrictions whatsoever. She repeatedly stole money from everyone in the house and lied about it. She frequently disappeared without warning, sometimes overnight. She lied, played one family member against another, etc. Basically just causing chaos however she could.
As others have opined, this was because of her life experience. Kids are phenomenally good at learning. That's their whole reason for existence, really. And what Mary had learned was that when things got tough, people got rid of her. After seeing how easily that lesson sank in on her second family with Mary, I shudder to think how well Padme has internalized it by her fifth family. Anyway, Mary figured sooner or later we were going to abandon her, so unconsciously she wouldn't allow herself to get close to us. She kept trying to push us away, to make us abandon her and prove her right.
That was basically life for us for a year. And after about a year of it, she realized that we weren't going anywhere and gave it up. There was never any formal cessation of hostilities or anything, she just wound down. Actually, "wound down" gives the wrong impression. Things
got much, much worse... and then they sort of stopped. And after that, things were pretty good. There was drama, but mostly of the "she's a 13-year-old girl" variety.
If I had to hazard a guess based on the (very, very) limited information I have, I'd hypothesize that Padme's behavior best fits this model. It explains why she's so loving to her sister: her sister is the one person she can count on not to abandon her, who doesn't demand anything of her or judge her. It also means if you give up on her, it just "proves" to her that her mental model is correct, and everyone really *will* abandon her when things get hard. Which is a really ####ty situation for you to find yourself in, essentially held emotional hostage to this girl's needs.
If I'm right, if there's no underlying mental disorder, then this is not exactly good news. Mental disorders are, in many ways, preferable. (Coming from someone with major family history of mental disorders ranging from depression to bipolar to dissociative identity disorder, borderline personality, you name it.) Once there's a diagnosis, there's usually some sort of plan of action. Things are hard, but the path is basically known.
Defense mechanisms don't lend themselves to a plan of action. Basically, the "plan of action" is "put up with as much #### as you humanly can". With no idea whether "as much #### as you humanly can" is as much #### as she's prepared to dish out. With no guidance on when the #### will eventually end, or even if it ever will. She might be irreparably broken, (think: your interaction with her biological father). She might be repairable but beyond your ability. You're a good man, but good intentions are a poor substitute for expertise, and your obligations will always be potential stumbling blocks.
We were able to weather Mary's ####. But it easily could have gone differently. Had she brought hard drugs into our house, or introduced my brother or I to them, that probably would have been a red line. Had my brother and I started hanging out with acquaintances of hers with gang affiliations, that would, too. Had she exacerbated my family's existing mental conditions in a dangerous way, the health and safety of my family would have taken precedence over her rehabilitation. We were incredibly lucky that she never crossed any lines that there was no coming back from. I offer no judgment for anyone in a situation where those lines *are* crossed.
One final coda. You might think my family is a success story, and in many ways we were. But also, in many ways, we weren't. Mary remained close with Sharon. Sharon was her mother. Closer, in fact; now that Sharon was freed from the obligations of parenthood, she was free to be Mary's best friend. They shared clothes, went shopping together, gossipped about boys. Sharon gabbed about the single lifestyle she was finally able to lead, and Mary considered it so glamorous and enviable.
My dad got a promotion that required us to move out of state. We discussed it with Mary and told her how much we wanted her to come with. She wanted to come, too. We had a house built and Mary would get a bedroom with her very own bathroom for the first time in her life. We promised to fly her back for holidays and summers so she could still see her mom plenty. Everyone was excited. Except for Sharon, who decided that having a daughter was actually so much fun (now that she didn't have to do anything) and who didn't want to lose her bestie.
Sharon waged a covert war for Mary's affections, persuading Mary to choose her instead of us. My parents refused to play dirty, because who wants to try to convince a kid not to love and trust her mother? Sharon eventually won, convincing Mary that life with her would be a non-stop slumber party. We moved. Mary stayed.
A while later, we found out that Mary had gone to visit extended family in California, and when she'd returned, Sharon had moved without telling her where. Mary crashed on friends' couches until eventually they kicked her out. Then she moved in with her boyfriend, who was 4 or 5 years older. She dropped out of high school, moved to California, and had kids really young. We lost touch, and I have no idea where she is today or what she's up to.
You could say that all of our time and effort was for nothing, but that's not really true. I mean, Mary still had us in her life for two years, and they were good years. My family learned a lot about sacrifice, and love, and also about how some problems don't really have solutions, but that doesn't mean they aren't worth trying to solve anyway. Because of this amazing thing my parents did, I know a lot more today about the meaning and shape of selflessness. They set an example for me to strive to live up to.
I have two little boys, age 5 and 1. Knowing what I know, would I take in a Mary of my own? Certainly not now. I don't have the energy or resources to commit to that kind of project right now. A decade from now? Who knows. Honestly, I'd probably be more likely to donate a kidney anonymously. Organ donation is quick and easy by comparison. It has a clearly-defined beginning, middle, and end-point.
But maybe. As you're seeing, there's a lot of bad that can (and inevitably will) arise from that choice. But sometimes there's a lot of good, too. Sometimes the good manages to outweigh the bad. And sometimes it doesn't, but at least you can go to bed at night and tell yourself that just because a problem doesn't have a solution doesn't mean you didn't try to solve it, anyway, and there's value in that, too.
moment for me when I desperately needed one. 
