T.H.
Does she still fit in an inner tube with leg holes? My son is 2.5 and he only used those when he was under 1. I would check the weight limit on them, but I have found some at Wal Mart and Target. I think maybe even Toys R Us might have them.
I don't personally think water wings are all that effective. If you really want to put something on her, I'd go with a Coast Guard approved life jacket. I prefer the vest ones, but I did see the ones, can't remember the name of them, that have a middle part and two arm holes and look very similar to water wings at Costco last week for $13, a very good deal on those.
All in all, I have found good quality stuff at Costco and Target for all my summer/pool/lake related needs!
ETA....just remembered...they are called Puddle Jumpers life jackets.