Should I break up with her or should I stay with her?

My best friend had this girlfriend that he treated her like complete shit. She and me started talking because she rants about him with me. I realized we have a lot in common like goals and we have chemistry and I have feelings for her. She lives with him in my native country and I went as vacation to visit her and my family. She is thinking of breaking up with him but if she does she has nowhere else to go since her mom don't want her back. So she was planning to but a car and move to an apartment and then break up with him.

The thing is that we kept talking and eventually she stayed at my home and we decided to give it a try. Now we are together and I'm going back to the country i live with her.

She said to me she was also talking with her ex while being with my best friend and she said she loved him and that she was in love with him, but apparently she says It was just an attraction.
But then I discovered she cheated on my best friend with her ex and told him that she loved him and that she wanted to spend her life with him and promised him many things. He is in love with her and she made him believe they were going to be together, and after all of that, few days later she told him to let her be happy and that he needs to leave her alone.
He destroyed that guy's dream. My best friend is a douchebag and he deserved karma, but her ex loved her deeply and wanted to try again and she made him believe that but apparently because I can give her a baby and marry her, she chose me instead, which doesn't make sense since she told him she wanted to marry him and have babies too.

All of this happened in less than 2 weeks.
Should I break up with her?
Should I break up with her or should I stay with her?
Add Opinion