I play a shiek about my level: here is some advice I can give:
1. use pills, but don't spam them. needles (and sheik in general) can just rip through them. Use them as mindgames and to appoach/retreat. DO NOT camp with them...Needles have a longer reach.
2. If your friend SHs, try to full jump over, and use n/b air. Shieks SH is kind of high still, so this puts you (well, me, but) in a position above her kick and at a range to avoid the claw. This doesn't always work, but don't let her get over YOU.
3.a As to when she is off the ledge and not directly below, bairing her once and grabbing the ledge works. This way she can only go so far onto the stage with her up-b, and the lag is enough to Ledge-hop another attack into her
3b. When she is directly below the ledge, I just wait for her to disappear, and then grab the ledge. This lets you avoid the possiblility of getting hit by the fire, and most likely she will be trying to go for the ledge. If not, she will be high enough over the ledge that you can agian just punish her when falling/landing lag
4. I like to just stay on the edge for awhile when knocked off. Either she tries to get you with her needles, to which you can just let go and grab agian, or she approaches you. If she uses the whip, then just punisher her for it...it isn't the best ledgeguard technique. Also, you can let go and up/use any aerial. The best thing is not to be predictable, just like with other opponents...
Hope this helps, but I don't play the best people (Though the shiek I'm talking about can beat someone who somewhat recently got 3rd in a local tournie, under koreandj and someone else)
