aerial or grounded? (or both, i suppose...) how are they affecting you? as in, are you in neutral and trying to position and shiek is just throwing out un/partially charged needles from the ground to mess with you? or is it as an edgeguarding tool and it's just stuffing up your options?
if it's aerial needles in neutral, you're probably making a bad decision and/or shiek is getting really hard reads on you.
grounded needles just involve a lot of staying on the ground ready to shield or being very precise about when and where you jump (for example, jumping onto a platform where you're at least relatively sure shiek can't punish and juggle you off of the landing). i don't believe fully charged grounded needles gives shiek advantage on shield, but i could be wrong (aerial needles, fully charged, most definitely DOES give advantage, though!).
if it's in terms of recovery, that's just rough. you want to recover as high as possible, which can be hard with shiek's fair sending low. otherwise, learn the arc and range that aerial needles can cover and try to not double jump within it, lest your dj be eaten. then there's the whole don't recover linear to the stage problem, with grounded needles : /
in general, against shiek, remember that her gameplan is typically to be lame and sit in spots that you feel really uncomfortable about and then try to make you do something about it. then, she beats your something that you just did. her dd game isn't that good (really short initial dash length. decent speed, but the length makes the dd not as useful as it is on, say, fox or cf), but she has a solid dash-wd/shield/crouch into tilt game.
you can outrange her, but she makes that rather obnoxiously difficult to do. stick to dtilt and if you go aerial to ground, try to stay safe with either ac nair into grab range (so you can start conditioning them to respect ac-nair-jab and then punish accordingly) or space out uair or rar bair (you can also try to be deceptive and space out ac-nair and go into d/ftilt, likely). then start using float if you think you'll get ftilted out of an approach or something like that.
aerial to aerial, you can outrange shiek, but shiek is going to like staying on the ground most of the time. fortunately, she doesn't move too quickly in the air, so you won't have the "nairplane" problem of a quick character throwing a fast, long lasting hitbox into you as you try to space an aerial. but, don't count on air-air encounters too much unless you've got shiek on tilt.
and when you do get to set up an edgeguard, MAKE IT COUNT. shiek is super easy to edgeguard, it's almost literally her biggest weakness. just start off with the edgehog and it becomes a (not really, but effectively so) 50-50 on is shiek going to land on stage or is shiek going to just keep going for the edge. if you think she'll land on stage, just ledge drop-land/wd and punish accordingly (there's enough landing lag that you should be able to wd past and grab into followup or tilt/smash to finish). otherwise, just hang out on the ledge, since she has no hitbox on reappearing.
sorry if i threw things out that you knew, i just tried to cover all the basics ;x
