I hate to say it, but her stash is worse than mine and mine's pretty darn bad. I know how she feels. It is just overwhelming and she'd probably rather piece her way out than fold her way out.
I agree with the others. Take one bin at a time and start ruler folding and sorting by color. I'd try to make the folds so that they either double stack in the cubby's or a single fold from one side to the other. A lot of hers looks like yardage. For me, I'd love to know how much is in each piece. If she does a lot of scrappies, she won't care. I like organized quilts, so I need to know the yardage.
Bottom line...anything you do will only be a help. She may not be able to help you, but will love you all the more for anything you do for her.