is she mad at me....?

Don't ask a person out on a dare, unless you actually like them. That way you can avoid hurt feelings from all parties. In terms of this girl, I would suggest you ask her if you can talk to her, and have a one on one about your feelings. She is upset at the moment, but I know she would appreciate it if you laid it all on the table for her. Tell her the truth - that you have no real genuine feelings for anyone but her, and that you truly want to begin a relationship with her. Good luck dude!

its your fault. you know that you are into someone and you mistakenly ask this girl out. if only your were loyal then this wont happen. maybe you can apologize to her in a very romantic way. you should also say sorry to the girl you joked on. thats is not good.

yeh...you shouldn't have done that even though it was just a dare lol..
that's how girls are

of course shes mad at you dude.

you shouldnt play with other girls right in front of the girl you like because that will push them away. even tho you were kidding, she took that seriously.

probably, now she maybe thinks that your interest has gone elsewhere.