Hi
I dont mean to sound harsh but this lady sounds like a narcissist. You sound like an empath. So together there is this toxic dynamic between the two of you.
I would suggest doing what narcissist’s hate – being held accountable.
She said her heart is what matters, not the circumstances?

Well then, why is it she wants to stay with the husband if the circumstances are such that she has invested time and effort into that relationship? And if her heart chose you, then why can’t she only choose you – her behaviour is confusing and toxic and illogical. It is actually damaging.

She thinks her feelings and her experiences are more valid and valuable than yours.

You can do better for yourself by taking accountability and responsibility for yourself, and not reaching out to her and feeding into her story by silencing your own story.

Best of luck dear, I believe you can do this, it won’t be easy, but empaths are strong 🙂