I think the answer to this dilemma is fairly simple. Granted, I'm not a cosplayer, but I do certainly have eyes, and an appreciation for aesthetics.

I think you're getting hung up on comparing yourself to her. Might be a good idea to do characters that are more suitable to you, rather than doing the same ones she does.

Yeah, she made a fantastic Leon, but the two of you also did different costumes. Mafia!Leon is less recognizable because it's an alternate outfit.

Sure, I know you like the same characters, but if you're convinced you don't look like the characters you're trying to portray and that she constantly shows you up at it, then the most logical solution seems to be to find other, more fitting characters to try a hand at.