I met a girl not too long ago who's really nice and fun, but she's way younger than me and I'm not super attracted to her. I met her sister, and her sister is exactly my type, a ton of fun, beautiful, and my actual age, too. I'm 99% sure my friend likes me, though, so it feels kind of impossible to ask out her sister, especially since her sister and her are quite friendly and there's a chance she (meaning my friend) may have mentioned she likes me.

Any advice, or basically just forget about it?