How can I get my ex girlfriend back? This is a little complicated please ladies only answer.?

My 48 year old ex girlfriend left me after her 26 year old daughter and I had a falling out due to her not following house rules, quitting her job, and bringing drama to my house. Day after our falling out, I discovered my girlfriend had been keeping in contact with her ex telling him about our problems, asking him if the rooms were ready, and telling each other I love you and I miss you. I confronted her about it and she said it was nothing and that she was just telling him what he wanted to hear so she could get her daughter and 8 year old grandson in there. I'm not positive but I think they all are staying with him. I don't think she loves him, cause if she did, she would have left me for him before now. I want my girlfriend back but not the irresponsible adult child. Ladies perspective how to go about doing this.