We aren't suppose to believe that she's going to be a model. She's a blonde with big tits, so her head gets filled with nonsense and she believes it. That, and she's kinda delusional. I could easily see her being a pornstar in season 3(if they make it that far), because her character fits the stereotype that falls into that category, while trying to become models.
She doesn't look old, manly, or ugly, not at all, she's just big and plain vanilla and wouldn't be a fashion model in any universe.
I didn't dig her character on Terminator, either.
There's a similar one that I like even less, she was the Jesus freak on ER, the pregnant landlady on Terminator, and is now on Cougar Town.
I'm not sure the producers/casting expect this woman to look like a serious fashion model, more of an unsophisticated white chick who thinks she is going places (and doesn't need to go to school, be nice to people, etc.) and thinks she's better than everyone she grew up with, and 20 years later she looks 40 years older and is smoking three packs a day in a trailer.