Yes, I can understand that as well. I'm not saying I condone her actions. It's just that I find her behavior understandable. The way I see it is this: She hasn't had any close friends except for Kevin. He's the only one who she has gotten close to besides KOS-MOS, so she doesn't really see the party as much more than acquaintances, which is why she treats them the way she does in favor of Kevin. It takes Allen's awesome speech to snap her the hell out of it, and make her realize that they really do care about her and ARE her friends.
I can relate to all of this, and I think I'd react the same way in her situation. I used to be kind of like her in the past as well. Does that make me a bit of a *****? Maybe it does. But when you feel all alone like that, and you've been alone your entire life, you tend to get really self-centered like that. And feel angry when you think nobody is helping. I have had a lot of feelings like she has had. Probably why I'm so biased towards her.
I like to think now though that she has learned from her mistakes, and that she's a lot better off, growing as a person away from that awful abusive man.
But I can't really say I am experiencing the same kind of weirdness. I only just bought and played it in around July or so of this year. After I played Xenogears for the first time. So to me, I've always been the same age as her. :P Yeah, I'm a new fan, but it was just such an amazing experience to me that I don't think I'll ever forget it.