Well, I understand what you mean. It's not that I dislike her, otherwise I would have rejected her. However, I did not appreciate the blackmail attempt. That scene really upset me. It took a lot of willpower not to reject her. Besides that, I do not find her to be as complex a character as others.
EDIT: One thing I really liked about Maddie is that she decided to find out if she's pregnant the traditional, romantic way. I'm expecting a great scene when that happens. Otherwise, I'm not convinced by the character at all.
Her story (like Alexia's or Megan's) in the family shows that the girls' lives don't revolve around Mjolnir or the MC. She wasn't part of the core family at the start, not even seen as family by anyone (except the MC on the romance path) for two seasons. But just like the other girls, once she starts interacting with the family, she "doesn't need" to be in a relationship with the MC to integrate. She has enough common points with some of the other girls to become a friend first, and a "sister" later.
The usual issue with the girls not living at home (Megan, Alexia, Maddie, Samantha, or Simone) is that their screen time is reduced if you compare it to Daphne, Emma, or Norah (f.e.), so the complexities should be subtler and shown in "events" instead of showing them in day-to-day interactions.
Maddie also has the problem that, usually, Zeus steals her scenes.
Maddie has one of those "big events" in the next update. The biggest scene I wrote in a while (or a combination of eight small scenes one after the other). We will know a lot more about her.
EDIT: About her pregnancy results: The timing is bad, because she will get the first clues about her pregnancy when the MC is in Aruba.