Samus can be a problem for Peach. But you can be a bigger problem to her. here is a few things I want you to work on if you want to get better at this match.
When you hei her off the stage, if she is far away and below the stage coming back, throw turnips. if they connect a good 2 to 3 times you can send her backing. If she is abouve you, create a wall of turnips and throw them at her.them when she comes down slowly, hit her with a N-air or some else to keep her off, If he is hanging on the edge, Float over it and do a FC to D-air, then N-ar her for the kil (time it)
when you fight her on the ground, at times you have to be evasive with her. watch for missles, its always good to have a turnip in your hand and follow up with a combo.. Use the FC techs, to take her out and make the match hard for her. Samus cant really do much about that. Also be patient when fighting her. Watch how the samus moves. watch how they aprroch you and all.
If getting comboed, DI away
If samus throws you down, DI away from her cause she will hit you with a N-air
Move alround alot, wave dash, Dashdance, and Use FC techs, try not to stay still so much. Confuse them in your movement
Watch for her missles, if you have to retreat go ahead and get some space from her, then you think you got it, go back into the fight. notying wrong with running away and getting space
Mix up your grabs and dash attacks.
Dont crouch cancel aginst samus too much, you will get owned for it hardcore.
mindgames buddy. Use goodmindgames to own.
this is all I have for you right now, anymore questions, feel free to ask, I'll be more than happy to help you