AITAH for not going to my homophobic sisters wedding?

I need some advice. My (23 F) older sisters wedding is in a month, and my girlfriend was never invited. i thought i could ‘tough it out’ and just get it over with, but with the day approaching it is just feeling more and more wrong. For context me and my girlfriend have been together 3 years, and living together for 2 years. I am so happy in my relationship, but still my family cannot accept it. After all this time the only progress we have made is i am able to bring my girlfriend around, but they treat her like a ghost.

I told my sister how it made me feel that she didn’t invite my partner to her wedding and she essentially said oh well i finalized the guest list. She then proceeded to tell me that my mom told her she’s not allowed to invite my girlfriend.

My sister and I have had a very rocky year, mostly because she doesn’t support me in my relationship, but other sister drama as well. I am not in the bridal party. This wedding is also a destination wedding to our home country.

My girlfriend and I were talking about this and about some text messages I sent to my parents drawing boundaries (if you can’t respect BOTH my partner and i, then I cannot continue this relationship) and she said she feels like I am valuing my family over our relationship, and if i go to this wedding she will need to take a break.

Honestly, I get her point. I want to treat her with the respect she deserves, and it’s not fair for her to stay back while I attend a wedding celebrating people that don’t even support us. But I just want to know, WIBTAH??