Sybil came to live with the Thompsons not long before Danae started her career as StarHammer. She always knew Danae was hiding something but couldn't figure out what. It didn't take too long to put all the pieces together but kept it to herself hoping that Danae would tell her when she was ready.
That moment never came. So Sybil was stuck with a secret she couldn't tell anyone. It was frustrating because in her mind it was so blatantly obvious. But Angela was barely home so the obvious wasn't immediately apparent. And Danae occupied her own world seemingly separate from the other two. Danae tried really hard not to acknowledge either of them.
Tonight, Sybil got tired of waiting and decided to force the issue.