How to deal with my friend?

There's this friend of my sister that I'm good friends with but lately, after she found out I liked her, I always feel like I'm walking on egg shells around her. She's quite the sarcastic person, and if I don't believe something she says/think she's joking, she'll get really mad. Likewise if I think she's being serious and she isn't, she'll get annoyed also. I have to watch myself when I complement her, else she'll get weird and angry. It's really annoyed me, but I want to keep the friendship. How do I deal with her?