Being in love with a "ghost"

Mara loves her flatmate Ron. He is perfect, but there is a small drawback. He is invisible. At least for other people. Only Mara can see and hear him. Unfortunately not more than that. She is convinced his conversations give her everything she needs to be happy. Ron thinks totally differently about that. He wants Mara to look for someone that can be with her physically as well. But Mara does not accept that at all. How can she convince Ron?