yeah, I'd be trolling garage sales, too. even if you don't see bikes, ask, sometimes bikes will materialize that they forgot to put out.
you're talking about giving your current bike to her, what size is it? is it even remotely suitable for a 5'0" 11 year old?
my daughter is now 18, she's about 5'6, she's all legs, too. she rides with her seat at the same height I do, and I'm 6' tall.
she's riding a older small aluminum frame road-bike Trek that has riser hybrid bars, and a long seat post, and she likes it alot. it has 700x25c road tires (currently Continental Ultra Gatorbacks), and zooms quite nicely. we paid $100 for this bike a few years ago from a local used bike store.