I'm so sorry ! But at her age of 27, there really isn't much you can do. I really feel for you, I really do and I agree that her choice is a bad one. She's only going to have heartache if and when he gets out. He's going to find it extremely difficult to find a job, being an ex-con so if she thinks he's going to be able to support her, she's seriously wrong. I'm afraid it's going to be the opposite.
If she does wait for him, she's going to have a very rough life. I don't know why he went to prison, but since it's going to be hard for him on the 'outside' he liable to go back to his "old ways."
Again, I'm sorry and my prayers are with you. God bless and please take care. Hugs, Lee