Quote:
It won't make me look arrogant if I say "Maybe you really do suck at it"?
How's this:
Yeah, maybe you really do suck at it =P jk, you're not that bad.
The important think is how you say it. Words give only 7% of the meaning. If you are playful, you have nothing to worry about. You can add "you're not that bad" only if you have seen her playing. Otherwise it sounds like you are trying to please her. The main thing is your attitude. If you don't sound serious - she won't take it serious. It's like a girl saying to you "Ah, you're such a jerk!" and laughing/smiling. Will you feel like she's arrogant?
Just have fun. Create a playful vibe and tease her a little
PS: If she seems to have low self-esteem or no sense of humor, then you probably shouldn't do it.