You did not say how old your daughter is but it sounds like she is still under your roof. That she feels comfortable communicating this with you is good and you should work to keep those channels open. She may (or may not) change her mind about this - it is my understanding that sexuality is not a “choice” - though it is not unusual for young people to “try on” identities as they grow into adulthood.
As long as your channels of communication are open, she will hear you.
Of note, I am a fallen-away Catholic who may (or may not) come back. I have a deep respect for the traditions (and miss them dearly), but can’t reconcile some parts with my beliefs - so I may not be the person to be offering advice.
But my words come from this experience:
I had a dear friend in high school who came out as gay after college. He was raised in a strict (very sheltered) Catholic home and struggled with familial acceptance after opening up to his parents. They were devastated and it is my understanding that his relationship with them was strained afterwards.
Sadly, he committed suicide later that year. I’m pretty sure they had regrets until their end days and would have rather had a son who was gay than one in a cemetery. Clearly there was more to his story but his parents felt they had played a part in the despair that encompassed his final days.
Whatever you do, please make sure she knows, in no uncertain terms, that she is loved and accepted by you. That you will always listen to her and support her, even if you don’t understand her.