i've been toying around with grabbing ledge..and then using my grapple to hit them..from there i recover accordingly to what the opposing team and my teammate is doing. its worked out really well when i have used it, but its pretty situational. bombs and UpB are really nice as well though. and to be honest, i think samus is awesome at saving teammates.
and if sheik is literally spamming Fair on your shield..you can WD back OoS and shoot a standing missile, or go charging in with dash attack/aerials, or take a step forward and utilt/ftilt
if shes doing SHFFL'd fairs WD OoS right past her when she jumps, and forward smash her from behind.
if she's doing FullJump Fairs, a nice one is WD OoS under and past her, and then run just a little bit further and then WD in place and turn around(do this so you end up right outside of her Bair range). this is a really good way to get an upper hand in stage positioning. watch out for turn around needles though.
or Nair/fair OoS and DI toward her. although i'm not the biggest fan of this one.
i personally like WD OoS in place and pivot fsmash/ftilt/dsmash.
from the exact spot that your saying on the stage, i don't like the use of Up B. the only place to go is to the top platform (where she can usually just fall on you with nair or something) or just back towards the edge (which is where your attempting to get away from i presume). and its pretty tough to edge cancel the up b on the bottom platform from the spot on the stage. so it would probably be my last resort.