Definitely go and see a lawyer.

Definitely don’t tell her about it.

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In a way, I am trying to justify her actions myself to understand why this happened better.

This is causing some of your pain. I’d recommend against it.

Imagine someone has just told you 1 + 1 = 3. Would you sit around for hours and days trying to work out how they got to that conclusion?

It is impossible to understand what doesn’t make sense. Leave her to her dumpster fire, you just concentrate on you!