Thanks for the follow-up. By any reasonable standard she lied and cheated. If she did not tell you she was sleeping with someone else while she was also sleeping with you, she "lied by omission" and it this day of STD danger, her splitting hairs over a definition is absurd. Herpes is another danger, and she could have passed that to you already without you knowing it.
Just because she wants to re-write history and make believe she's blameless doesn't mean you have to go along with it.
Don't even bother debating this with her....don't stoop to her level. She endangered you without your knowledge...that's all the information you need, I would think Does she seriously think a "definition" is more important than that?
I'm sorry to hear there are children involved....otherwise I'm sure it would be easier for you to just walk away. It may be time to get a lawyer to protect your visitation rights.
I don't see how you could trust her in the future...you'd have to carry a dictionary with you at all times, and get her to define everything she says.
Sorry to be so brutally honest, but this seems a very cut and dried case of someone who cannot be trusted.
I wish you the best,