If your girlfriend hooked up with another female behind your back would you consider that cheating?

I hooked up with my female best friend and I’m afraid to tell my current boyfriend. I’ve been feeling very guilty because I thought okay if it was me with a male? He wouldn’t like it, but is it the same if it’s a female? I know some men that are serious might not like the idea and some might find it attractive (Is this love if they do?). I need honest answers please.
If your girlfriend hooked up with another female behind your back would you consider that cheating?
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