Platforms aren't Peach's friend? What?
At certain percents vs ffers, you can dash attack or uthrow them, and if they land on a platform, it creates some stupid games. If they don't tech immediately, you get anywhere from 2-4 free uairs (depending on DI, percent, etc). If they do, you can use her djc trick to punish teching towards you or in place, if they tech roll away, you can dash attack and if they block, they get pushed off the platform (and dependend on shield DI/the stage, they can fall off the stage entirely). If they don't, free combo.
If someone is overly gung-ho about approaching you while you're below lower platforms (bf, ps, ys, etc), you can jump up to one when you see a spacing error, and dsmash them for pretty dumb amounts of damage. Good players can bait and punish it, but hey, you gotta know how to wipe out weaker players, too.
If you're standing below a low platform, you can also shut down most angles of aerial approach using turnips, fc nairs, and dtilt/usmash (my favourite). Can also be baited, of course.
I posted some quick tips on your video as "izzyinfamous". I didn't have time to watch the full thing, though.