I am glad to hear that you are trying to reconnect with your sister! I hope that continues to be a positive experience for you.

As for the woman you met, I am SO sorry that she treated you that way. I would be confused and upset too. If it was me, I would not see the person again. Anyone who starts a new relationship with a lie is not worth having in your life. Even if she and her boyfriend have an "open" relationship, she should have told you that from the start. And, unfortunately, now that you know that she didn't tell you the truth about having a boyfriend, you really don't know how much of anything else she has told you is true.

I also have trust issues, so I do know how hard it can be when you finally do start to trust someone and then they shatter that trust. It is 10 times more difficult to trust again. I do hope that you will someday meet someone who can earn your trust and keep it. Take care of yourself and do whatever you feel is right for you.