Fly, do you remember the name of the Peach I MM'ed @ ActiveGamers? I'm pretty sure a few people watched the set but I dunno if you did.
Your Samus advice is pretty sound, really. I'll be honest though, I wouldn't mind approaching a Samus at the edge because you WANT her to d-smash your shield. Punish it with WD out of shield into grab, and she's at the edge for a handoff.
Try approaching her backwards. This gives you lots of good opportunities.
1) It baits smashes more; WD out of shield is not commonly used. Approaching backwards into your shield WILL make people more aggressive against you. Against Samus, her d-tilt, d-smash and f-smash can all be punished with WD into grab.
2) F-tilt is punishable from shield with short hop b-air.
3) Sets up the tilt-guard de-sync. If the Samus is trying to completely zone you, you can wavedash outside her range, tilt, and then bring up a blizzard. If she tries to reach into it, she has a high chance of eating a smash or grab afterwards.
Against missiles, especially when Samus has higher percent, wavedash in and f-smash. You get hit, Nana does not, and her smash follows through on your behalf. I catch people DI'ing badly all the time like this, and it can give you crucial KOs at (relatively) early percents.
<3