Not sure, as I'm an atheist and none of my theist relatives are catholic.
But I know this is a catholic church and she is a (or maybe the?) priest there. It's also possible that I could be getting my terminology wrong but she is definitely not a nun. This place is right in the middle of the TL and I believe functions mostly as an aid for the homeless of San Francisco, they close their doors some time in the afternoon. So yeah, I don't know enough about the catholic church to know what is or is not allowed I just know what I see and am told.