it doesn't take much for marth to gain momentum either...
all he has to do is put you in the air and safely cover all your options
the only thing i would say peach has over marth in the matchup is her gimps
aside from that she has nothing that stands out
if she approaches from the ground you know it's going to be 1 of two things
either DA or grab
DA can be shield grabbed
and grab can be spot dodge downsmashed
every attack she hits your shield with (bar projectiles) can be UB'd, her reach is terribad
she can't out-camp you and can't juggle you half as good as marth can
her approaches are **** tbh, doesn't matter if she's FC things into jab, you can just UB w/e she hits your shield with
not like she's going to come down with a grab, and even if she does an empty jump/float, just UB when she's in your vicinity and you'll get her grab too
her punishes are garbage as well
dsmash is a non issue, and her shield pressure is too if you light shield or UB
peaches kind of give me a hard time though because all the hard counters to her **** i don't like to do; ub OoS, camp, not approach.
now if you try to approach the peach through her turnip bull**** and fair float camping you might run into some problems