I started using this after noticing a definition of frail: "the weight of a frail (basket) full of fruit, esp. raisins or figs (between 50 and 75 pounds)."
All the implications of frail (mental, moral, or physical—'fragile, easily destroyed or broken, weak, insubstantial'; slightly offensive slang term for 'girl/woman'), fruit, and basket(case) can be rolled into this expression. Especially well-suited for women who've made themselves crazy (or physically weak) with dieting. Or thin, crazy women in general.
For variety, when you're feeling particularly spunky, the number can be anywhere from 50 to 75, and 'raisins' is interchanegable with 'figs,' 'dates,' 'fruit,' or any kind of fruit that might be dried and stored in a basket.