How to deal with gf who's not over with her ex yet?

My girlfriend is not over with her ex-boyfriend yet and I don't know if I should let her go because of that or help her move on and wait until she finally loves me for real. When we go out on a date, I sometimes noticed her thinking deep while looking at her phone. She sometimes reread her conversation with her ex. When we were eating at a foreign restaurant one time, she only stared at her food, probably thinking something from the past. I even don't know if she's happy being with me. I never heard her say she loves me. I love her but this relationship is not healthy. Should I let her go now?