Yes it's cheating technically. But she's obviously too nervous to tell you about it. Will you support her doing this? Can you talk to her in a positive way about this? You will have to be the one to start the talk, she won't as she's too nervous. She sounds like she's bi.
So, let's make it "not cheating" by you talking about it with her. Maybe you can make this work, if she will just be honest about it. If she's not honest about it, then you know you are dealing with a liar who doesn't have to courage to be herself.
I have a long time interest in psychology, specializing in relationship dynamics for 30 years.
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