Nair is the only approach move that can work on Sheik. Problem is, she can CC grab that to obscene percents. If you notice this keeps happening, *then* you mix up the stomps and knees, meditatively, of course - not without discretion. Some Sheiks are very ground based (i.e., Drephen); they'll grab, dsmash, dash attack and ftilt all day. Those are the sheiks that you need to be grabbing. Note that all the moves I stated are punishable with well timed JC'ed grabs. Jumpy sheiks can kind of be dash dance camped, but it's better to be aggressive against those types, like with run up raptor boosts, uairs and nairs.