Confused please help: Relationship Advice?

I am 32 Male from South India

She is my would be wife. When she met me 8 months back she told me that she want to be honest with me and so disclosed that she had a past. Her lover is in same city in which we two are working.

She assured me that her past is past and she will never bring it in our present but she needs some time to forget her lover.

Now I respected her honesty and gave her time of 4-5 months. The problem is she is constantly demeaning me and my feelings by bringing the name of her lover. that if he would have been there he would have never treated me like this, no one can love me more than him and what not.

Every time she says to me that she is going to meet him for the last time, but she meets him as she prefers to live near his house rather than mine which are at different ends of the city.

Now since I am far I cannot be always available to her and she is relishing the time with her lover assuming that I m fine with it as she will be mine completely after marriage.

Few days back she also confessed with me that she had physical relationship with his lover on regular basis for so many years so I should understand her that it is difficult to leave a person after that and thus I should give her more time.

I assume that the physical relationship is going on now also.

Can this girl be trusted at all. I loved her for her innocence and honestly but as she continues to bring her lover in the present, I am worried she will never change, not even after marriage.

Though I lover her, but I am unable to imagine her as mine, pictures of her sexual encounter with her lover are coming in my mind the moment I think her.

Please advice, If I am on completely wrong path and this girl is hopeless.

P.S She cant marry that guy because of some family issues which cannot be resolved