My opinion is that Twist was a character that seemed like a good idea when they came up with her, but didn't really add much to the series overall. In my mind, she doesn't really have any memorable lines or scenes, and her only interesting bit was her torrid relationship with Brian.
I recognize I may be alone in this opinion, so I'm willing to hear yours.
Gentlemen, you can't fight in here! This is the War Room!
She tied the group together. I think women might understand this more than men. It's kinda like politics. Brian is just a neighbor. Tim even says right out in an episode that he doesn't like him and he is pretentious. The episode he punches Brians old partner, the weird stage performance one. Daisy invites herself and Tim (women are better at that than dudes), and Brian doesn't quite like them either, but feels more comfortable around them than vice versa. After that they become more friendly. But they aren't true friends until Twist comes along. It takes a friend of Daisy's to pull him in to the tight knit group in a way he either never would, or would have taken much longer for it to seem realistic. It's related to a concept I've learned in late 20's dating. A woman wants to date a man for his friends. They want to feel like they are living a sitcom. Or reliving highschool. It's a social thing. The bigger the group the better.
shareShe added a grounding element to Brian.
She brought him into the realms of reality and made him relate-able to the viewer. Brian became a person rather than some abstract characteur.
Hope this answer was worth the 6 year wait <_<