Ex & I trying to get back together - How can she get rid of her current gf?

My ex girlfriend and I broke up 2 yrs ago. Im a . My Ex, D & I were together for 4 yrs. We didn’t break up because we didn’t love each other it was just becoming too unhealthy. At the time I was drinking and partying very heavily ( I was 23 & not looking to settle down) I was also hurt by her leaving me a few times for her ex at the beginning of our relationship so I had major trust issues with her. We broke up for good 2 yrs ago & we both entered in serious relationships. Dee has a healthy relationship & is comfortable w/ her situation. The only problem is we are both still in love with each other. My relationship was somewhat turbulent & not good on many different levels. I just left my ex 2 mos ago. The real issue here is that I love Dee so much & I miss her just like she misses me. But she is scared to get rid her “stability” for me even though I told her I would marry her tomorrow! Also, her current gf moved here from another state so she