The altar coverage is very small, just maybe half a floor piece wide. You will have to supplement with a roof/floor that will get broken. Keep a workbench under there so you can put it back up. That way she won't see you when flying. Could also fit a fire under there to get rested back if you need it. Make it easy to get in and out so you can get her while she's on the ground. If you are under the altar, she will likely land on top of it.