The idea that someone is driving by the house and firing 3 shots is not realistic so we sort of know that it's not real. At the same time they make sure to frame it like its possible by having Mike around. The paper tosses I thought showed that it was all in her head to the audience.
That actress is not so good, super weak compared to the rest of the cast. Easily the worst actor/actress with more than a couple lines in both BB and BCS.
The character, not the actress, is the one whose acting is not so great.
Mike's daughter-in-law isn't going crazy. She's
lying. She tells Mike that there are gun shots because she wants him to get her a nicer place. In her scenes with Mike, in the kitchen and in the driveway, she was acting. Not well, but what do you expect from an amateur?