<human>: My sister got engaged a few days ago and I am not happy for her at all. Her fiance is Baptist and my sister decided to "convert" for him a while back in their relationship. I say "convert" because I don't think she is officially apart of their church. 

The thing is, my sister was a proclaimed atheist before they got very serious.When I asked her why she was switching over to Christianity, she just said that she was lost and it helped her somehow. I said why not another religion and she told me that she looked into them but Christianity was the best for her. She couldn't tell me why though. I am all for spiritual guidance, but it was obvious that her boyfriend had something to do with it. I decided to have a conversation with this guy. 

Some of the things he said:

"I could not marry your sister if she was not Christian" 

"You're family is messed up because you don't have God in your home"

These are some of the gems that stuck out to me and I can't get them out of my head. My sister wants to marry this guy! No one on my side of the family approves, he is not even allowed inside our house. They are also moving in together and when I asked her how she was going to pay rent she said that she was "going to work at a bar or something". She does plan on graduating sometime in the future. 
I am so worried for my older sister. I don't want to lose her, but at the same time I already feel like she is such a completely different person. What should I do/not do?

Could you distill the essence of the text into 1-3 sentences?
<bot>: older sister converted to be with her now fiance and no one in my family approves and/or is happy for her or likes the fiance.