How to deal with a homophobic friend?

My friend is homophobic. She is not a "raging homophobe" but she does not hide the fact. She is a very conservative Catholic and I know that does not excuse her, but I get why she is. It really pisses me off when she is homophobic. It would be one thing if she kept it to herself but she doesn't.

Just the other day we were in the car together and she said something about how "she wasn't against LGBT" (she was obviously trying to reassure herself) but she during a lecture in class she saw two girls kiss and went on about how she didn't want to see that. Ugh. It made me mad but I just went 'mhm' hoping that would end it. But she continued about how if it was a boy and girl, they would have gotten sent to the office. I just told her it didn't matter and sort of ignored her.

She's a pretty good friend and I'm lonely so I just want tips on how to deal with it. I know I'll probably snap eventually if I don't know how to deal with her homophobia.