Why is my cat so freaked out when my other cats try to play?

My 4 year old cat Mya has gotten a clean bill of health recently so I don't know what could be causing this. Whenever one of my other cats (I have a total of 6) tries to play with her she'll scream really loudly and run away. When she screams it sounds terrible, like she's in alot of pain, but she's not. Sometimes she'll initiate play with the other cats, but when they go to her, she freaks out. What's her problem?