This is so stressful

I M26 began seeing this girl F23 a few months ago. She is in a relationship with another women but she hasn’t left her because the other women threatens to kill herself if she does leave.
I began to see her knowing her situation but I expected that she would finally get the courage to leave this girl. We spend every night talking and she has come over and we have had sex multiple times.

She has finally said to me that she wants to leave but she still can’t as the girl keeps threatening to kill herself and that she will actually do it.

Today I broke things off with her because I said to her you need to leave her our relationship can’t progress until you do. She’s still too scared too.

She knows she is being blackmailed and manipulated. Yet she still stays I don’t understand why.

I’ve broken things off and I don’t even want to but I have to. I am so upset about this because we both like each other a lot. When I broke it off she seemed very uncaring however she bottles up her emotions a lot and doesn’t show any of it.

I’m so confused and I just want some advice. I want her so badly, but she won’t leave this girl. How can I wait it out and not let it effect me so much and did I make the right decision?

Please help