Now I have to re-watch again, because I completely missed her saying anything about that to her mother. The first time I remember it being mentioned was when the video of her beating up the guys who were about to rape the girl that was with them comes out, Starlight's handler reads one of the comments about her, and it includes the line "I knew her in high school. She was bulimic."
We've already seen A-Train 'juicing' with Compound V, it will be interesting if we see Starlight have more scenes where she's vomiting, and what leads up to it. So far, both times they've shown her doing that, the reasons have more or less been justified--first after The Deep took advantage of her, and then again when she was drunk at the party when she was flirting with the sailor. It seems to me that if she has this dirty little secret that she's been hiding, as opposed to her trips to the toilet being more caused by something she has no control over, I don't see her pulling off the 'virtuous' vibe she has. But I guess we'll see.