I'm going to delete a facebook message so my fiance wouldn't get jealous and mad
What did the message say anyways?
It was from a girl named Jasmine who said that she liked me.
I think that you should just tell her, it is not like you responded or anything. Lying about it is just going to cause more problems when the truth comes out.
Maybe I shouldn't delete the message then.
I think the correct choice would be to tell her about the message and show it to her so she can see it, and then delete it. That way she knows you were being honest and upfront with her. Keeping this a secret from her can come back to bite you if she finds out about the message from someone else.