Ban Jungle Japes, no questions :O
A good Peach should know how to DI your fsmash and if she isn't playing risky at the edge platforms, she lives for a WHILE :O [and with proper DI, that is a LONG LONG time :O]
Most of her kills will probably be at the sides with her aerials [all but uair] and she really isn't going to kill you vertically ever unless she gets in a sweetspotted usmash, which should have enough power to vertical KO [assuming decent percentage] if it hits while the stage limits your horizontal kills with fsmash [not saying you can't get horizontal kills otherwise, just not with fsmash] and 'nerfs' your vertical kills with it's amazing ceiling :O
The flowing water refreshes our float, and autofloat is instantaneous, meaning Peach usually won't die there :O but same goes for tlink with his good recovery and jumps [just avoid the claptrap >___>;;]
Peach bomber auto grabs the ledge when it misses, if you're at the left edge of the stage, Peach's edge guarding game can lead to an early death, the platform allow for easy utilts, etc, etc
This stage is just too good for Peach, ban it :O
other than that? I'd counterpick stages with low ceilings for early v.kills or stages that allow you to abuse your amazing projectile game :O
or a stage that has both if there is one?
Peach really doesn't have a 'bad' stage, so I'd go with stages your comfortable with :O
which will hopefully have low ceilings :O
and to ban stages with high ceilings, as the longer Peach survives, the worse it gets for you :O
Personally, I absolutely HATE Lylat [why does it have to be neutral? DX] and dislike Yoshi's Island :O [though, it usually doesn't affect performance too much, I just dont' like them :/]
Be careful: even though Lylat may reduce our ground float game, it makes our tilts AMAZING :O
and the tilting of the stage can be a hindrance to your projectile game as well
Different people have different feelings and results with the stage and some Peaches seem to rather like it, as float is always horizontal regardless of tilting, 'tiltalicious,' etc
your call on Lylat :3
Main point: Ban JJ. Always. o.o
Counter Pick stages with low ceilings that you're comfortable with :O
try out Lylat and Yoshi's Island if you think it'll help you and your playstyle than it will help Peach's [as each has their own preference :3].
[but again, stages that you're comfortable with]