What do i do in an awkward moment because my crush knows i like her?

Unfortunately for me, my little ***** sister who i hate so much who cries all the time (she is ******* 12 years old), snitches on me when i do something wrong, and gets my dad to always yell at me for the stupidest things has finally crossed the line and chatted with my crush and told her that i liked her =( i am a really nice guy i never cuss unless im like breaking apart completely mad and so she told her just because she said in the message "Revenge on my brother chris, he has a crush on you". so any ways here's my question,1. how do i like remember not to ever talk to my little sister and 2.what do i do in an awkward situation like if she says "hey do you like me because i dont like you." or if she says "DUDE i DONT LIKE YOU OK??" should i say something like um i said u wwere cute but not anymore or what do i say to tell her i don;t like her.