What to say if you didn't invite someone to your birthday party?

Now, I am having a 2-night sleepover for my birthday party this year. I couldn't invite many people cause you know birthday parties get expensive. So I invited 5 people. I didn't invite these two girls that I was friends with through out the year. These two girls are twins so it would be rude to invite one but not the other. One twin (I'm gonna call her "E") was my "bff" but then she started treating me like crap and talked bad about me through out the year and was just plain nasty to me other times. She once told me that I didn't have any friends and nobody liked me and that i was ugly. She also told my crush some untrue things about me. The other twin (I'm gonna call her "A") is currently mad at me and has deleted me from her Facebook friends. She's mad at me because I "stole" her "best friend" away from her and I made the cheerleading team and she didn't. Anyways, I get a text from E asking me if I'm having a birthday party. I didn't respond because I didn't know if I should just tell her that I didn't invite her or lie. PLEASE HELP ME!!!! I need to know what to tell them.