I lost my girlfriend to another man

Dear dr Leo.

We have been together for 4.5 years. She has been my best friend. I never doubted her and I trusted her when she told me the man she is with now was just a close friend and she only had love for me only. She has now left me for him and she has chosen him over me. She told me she loves me but she is not in love with me and he is the man she loves now. They are in a relationship while am being badly treated like trash. I feel bad because she has been lying to me for such a long time and it hurts so badly because I care much for her.

Is there any way you can help me get her back from him or any kind of advice that will help me to get her back.