I feel like they don't know what to do with this (awesome) character herself, actually, let alone her background. I do wish we know more about how she is what she is, but considering she's a lead, they seem to be fumbling with giving her more dimension. They keep giving her love-life-related storylines, and while I love her with Jesse and all, and I understand that the underlying emotion is that she feels lonely, what else are we getting from her? It's repetitive and totally unfair to her, I think.
and don't know how to write the background that would have created her.
I think Lea could play anything she's given, and I think Rachel could be so much more interesting if the focus is more on other aspects of her life. As it is, I adore Rachel, but I'm tired of seeing her being relegated to one-note storylines and being hated on by the people who watch the show for those reasons.