Hmm not much of a Sheiker myself, my Zelda is far better, but dont underestimate needles
In reponse to the switching to Zelda:
Zeldas is a really good option in this matchup at ~90-100%
Simply because she doesnt do too bad against Mario (you guys decided on 55-45 Mario adv. right?) and she just has to wait for an opening to get a kill move in (its not too hard she has too many and outranges Mario -.-) Its key that her kill moves are fresh too, because where Fsmash or Usmash usually wouldnt kill they will now.
Im not gonna debate going all Sheik though, not too knowledgeable in that aspect. They are simply better played together in a lot of matchups, minus like MK, Snake, Olimar, and GaW (Zelda's **** matchups). So if you were gonna put a ratio on Sheik/Zelda used together, Id put it slightly her than solo Sheik. I wanna see what solo Sheikers have to say though
@Inferno: Im guessing your opponent was probably worse at Zelda than Sheik or didnt know the matchup too well. Its not surprising, most Sheik mains dont put much effort into Zelda besides being character specific like IC, which is sad considering they compliment each other so well.