Peach is certainly not (relatively) easy. At least, from my experience. Then again, I haven't played Melee long and only once against a good opponent (and that were only 2 matches). But still, I can tell she's pretty hard.
Ps I should visit my sister board more often.
Honestly, I've worked on Marth, Sheik, fox, peach, and Ganondorf as secondaries over my melee career, and out of them, Peach was by far the easiest to learn.
It's not even so much that Peach is an easy character, it's just everyone else is much harder, she doesn't (or has relatively little use for) a lot of the universal techs and her individual techs are a heck of a lot easier then waveshining for example. Granted, she has spacing to deal with like everyone else, but honestly comparing the work I put into learning every character, I've put the least time into learning her, and she's the only character that I have pretty much every skill down for, now I just need more experience.
Even sheik, another easy character, my peach is MUCH better at the skills of the character.
My marth, no contest, even though I'm probably slightly better with him overall, but that's because he's a better character.