Uair and Nair both cover Peach above her; you definitely don't want to be there. Directly challenging her float isn't totally awful if you don't anticipate her to nair you since your fair is much faster than hers, but once she starts to catch on nair becomes too risky to try and beat. If she floats low enough you could try to contest with a ftilt but those tend to just trade with her dairs or fairs if she times them correctly. Being behind isn't very good either since her bair will always trade or beat your moves; I think it's one of her best tools in the match up. Honestly I'd just get on a platform and try to interrupt her float with needles or just wait for her float to end. If you watch carefully when she throws out her aerials you can anticipate whether you can punish her landing even if she attempts to float cancel. I haven't look at much frame data for float canceled fairs from Peach, but I wouldn't be surprised if a perfectly timed one would have an extremely small window of opportunity to punish before she can act, so be careful of that.