I'm sure a Christian church will issue a fatwa on her...oh, wait a minute...
When she is married to the muslim, and he gets citizenship, I'm sure she will survive the honor killing. Then again, anything can happen.
Sorry, I lived in the Middle East for almost two years.
5.56mm
I would tell her, even though it will do no good. No harm will be done she will not be a friend any longer to you when he is done brainwashing her anyway.
The harder you speak against him the more she will be defiant about it.
Obviously her parents have spoken to her about it and deepened her commitment to do just the opposite.
One day she may learn her mistake, after a good beating or acid thrown in her face or she tires of wearing a Burka. She may come out of it dead. Her children will be Muslims, and if they separate he will take them to some foreign craphole like has been done so many times.
Once she knows the facts and chooses to ignore them she is on her own.Wish her the best of what will be an unhappy life.