I also had once the same doubt as you. My ex was christian and I was a buddhist.

at the end of the day it's about compromising. if she's ok following to you to pray at the temple then its ok. if you're ok joining her for weekly church activities or worships, then its ok too.

anyhow our relationship did not work out in the end.

best of luck to you TS. Sometimes I'm not even sure why we limit ourselves to religion when it comes to love