Listen, they were not that original, or well written. But they worked. There's no such thing as an "original" plot. Everything has been done before. Stephanie's characters are pretty plain and her plot is in Twilight is not that strong. But (for me) I was able to look past these flaws and enjoy the story which I found enjoyable, fun and easy to read.
Yes, Bella does get obsessed with Edward. Yes, she does sacrifice a lot for him. Yes, one might argue that she might not be the best role model for young girls. But who says she has to be a role model? She's a fictional character. Since when do fictional characters have to lead by example? When did their actions become so important? Who decided they should be role models to young readers? Can't characters be flawed and make mistakes and questionable decisions?
"Concern trolls" almost act like Bella is the anti-Christ. They are horrified by her decision to be with Edward who they think is a stalker and abusive (um, why? how? He was nothing but polite and patient and gentle with her). They see Bella as a cardboard cut out who any young girl could easily imagine themselves as. They are concerned about her relationship with her parents and how she has trouble making and keeping friends (other than the Cullens) and what terrifies them the most is her decision to let her life revolve around Edward rather than leading a human life, going to university, etc.
They think Bella and Edward's relationship is sick and twisted and that is makes abusive relationships dangerous and exciting and glamorous.
Okay, firstly, in my opinion their relationship is not abusive: Edward spends most of the first book trying to avoid Bella. Yes, he watches her at night, I can see how some might find that creepy, but that is a fantasy people: stop taking this shit so damn seriously! I honestly feel like people get too worked up about Twilight and over analyse it and find creepiness where there really isn't any.
It's just a book, people. Young girls are not idiots. They know it's not true. They know abusive relationships are not fun (not that I think it was abusive!). These books are escapism, fantasy, nothing more. Stop getting your knickers in a twist. Because I'm tired of all the whinging and "Someone think of the Children!" shrieking.