I havn't faced one recently, but I moved her down on my guide a couple weeks ago when I realized how slow and punishable she as, as long as you don't rush right into her attacks. Avoid Falcon Kick, as it sets her up almost perfectly for a FAir/BAir, and be careful about trying to follow up because of the power of those moves. Her DAir has some kick to it but is very hard for her to land it, so UAir away, but don't try to juggle her higher than a full hop because she can up-B back to the ground. The last few times I'd played Sheik was giving me a much harder time than Zelda, mostly the dang FTilts, Needles, FAirs, and up-B kills (I think it's called Vanish?).
The problems I have the most with Zelda are her DTilt, DSmash, and USmash, because DTilt is pretty fast and trips, DSmash makes it hard to stay close and knocks you back at a pretty bad angle, and USmash stops all aerial and several ground approaches. But she's really not that bad. Once I play another one I'll most likely move her down some more.