Have Relationship Questions? Ask a Counselor for Answers ASAP
There could be a chance if she wants to get back (and she would need to tell you that not when she is under any influence of drugs or alcohol but sober) If she is actively dating the other person, then she would have to stop seeing her before you and her get back together.
Her feelings being changed towards you is not unusual. You've been apart, grown emotionally and she's fallen in love with others while you were separated.
As far as strategies to get her back you have to be open with her about what you want, be flexible (give her some time to figure things for herself) and when you meet her again make sure when you talk or interact with her that she is sober.