If my girlfriend got intimate with another woman on my b-day, that's still cheating right?

Two months ago was my b-day and she came late. I just found out she's been with someone else but I'm not sure how to react. It wasn't with a man. It was with another woman.

I knew she was bi but we agreed to be in a committed relationship as I'm not into sharing. While I don't feel that threatened by another woman, I still felt she cheated.

If a woman gets intimate with another woman it's still cheating right?

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1 y
I guess I won't ever date a bi woman again. She's trying to call me but I'm currently ignoring her calls. While it was hurtful what she did on my b-day, I feel awkward about this situation. I'm still hurt but not as devastated as if it would've been if she was with a man.
If my girlfriend got intimate with another woman on my b-day, that's still cheating right?
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