very common problem with buttons. They jump up when startled and hit thier heads. It's important to have them in a cage atleast 3' high or have some padding on the top. I use a wound powder on such injuries. Yours looks like a bad one. Since she's still alive try some wound powder and keep her in a place where she won't re injur it. They have a main vein running across the top of the head that if they rupture that they will die almost immediately. Some bash up thier heads bad and don't get that vein and another can scrape the top off the head and recover fine too but sometimes they rupture that vein and they don't make it. Prognosis is good if she's still alive. They seem to be able to bounce right back from it.
Their cage is like 15" tall, but shes a jumper. I think the male might have had something to do with it. I treated it with veterycin last night and she is actually doing great this morning. Eating, drinking, and acting normally. Just a LOT of blood freaked me out yesterday. She seems fine now though...just a bit scabbed up. Thanks for your response!