Ask your mutual friend if this girl is part of any weird Christian sects.... met a Math Phd who was Wisconsin Synod (she was totally bonkers and not in a nerdy type of way.)
Just a red flag, but it could be nothing.
If not, then it was just one of those little awkward things.
(Note in regards to Tiruin's post: Some nondenominational sects (and the sect I mentioned in particular) require doctrinal conformity and can be quite radical. This girl I met in particular was homeschooled and her parents quit their jobs and moved 200 miles when their old church closed just to be part of the same Lutheran sect. That and some splinter groups from the ELCA are also quite particular... Generally, by weird, I mean the group is openly bigoted towards homosexuals or vehemently denies evolution / has an uncompromisingly rigid doctrine. Some Christian sects are quite stringent on what constitutes their "in" group and "out" groups, if you become involved with someone who has such group definitions, they might want you to join said "in" group because their doctrine requires it, which may or may not be alright depending on one's own belief system. Sorry for the off topic tirade.)