Evvie didn't need the demon to tell her to participate other than the fact that the screaming broke her out of her stupor as she stood completely baffled in the face of the current events that included a random caveman fighting the cave (didn't cavemen like caves?), the cave somehow collapsing underneath his strikes, and the teleporting opponent. All in all this was turning out to be a very strange battle, which she actually enjoyed every once in a while to make things more interesting, only if it got too strange it would make her head hurt. Hopefully nothing else strange would happen to overload her poor brain. 

She breathed fire into her right hand, which she quickly began to mold into the shape of a 4 foot long sword. She'd need a bit more time to finish the shape and solidify it so that it could deflect her opponent's own sword, but even though it wasn't finished yet it was still a deadly flame extending from her hand and could be used to perhaps fend the man off for the time it would take to complete it. On one hand she could wait until it was completed before charging in, but she didn't exactly have the patience right now, wanting to take him on before he moved on to someone else and did too much damage. Not that she didn't have faith in her team, but she wanted to try her luck at taking him on herself, especially when it was clear that they were counting on her to do something.

As she rushed forward she ignored the caveman, not sure exactly who's side he was on due to the confusing nature of his appearance and actions so far. She went straight for the other guy who had directly attacked her ally, obviously the more serious threat here. If she was able to get close enough without being interfered with she would swing horizontally from right to left that would strike through his upper torso if he didn't do anything about it. Due to not taking on a solid form it wouldn't cut through him, but he would suffer a horrible burn going across his body that certainly would be far from pleasant. 

She couldn't solidify her sword while doing this, both if she couldn't concentrate on it and if the fire was interacting with physical mass such as his chest, so if this attack worked in fending him off for even a brief moment she would use that time to concentrate on giving it solid form rather than press the attack even further unless a clear opportunity presented itself.