Demonic possession is stupid, yes, it continues her cycle of abuse and robs her of agency and influence.
No,it is not. It is one of the highlights of the game,we are talking about the shadowrun world,a place where magic combines with modern society. Is it that strange to you that the devil could come up and fuck up people? Or is it just a butthurt atheism?
It's not about atheism or anything like that, but about one simple question - does making her be possessed by the devil or being an abuse victim make her a better character?
All too often, video game writers (and not just them, unfortunately) confuse character traits with having actual character. They start with one (or more) fantastical element(s), which they then blow out of proportion - instead of fleshing out the characters themselves - until that is all that's left.
Which is, I feel, what happened with Glory. They had a good idea for a compelling character, which they pushed to the point of predictable cliche. Toning her down a bit would have been far more interesting.