Okay, this is a difficult one because there are many movies about mentally ill people falling in love. I remember this one had actors who looked like Chris Klein and Helena Bonham Carter. I'm not complitely sure though. The man went to some therapy group and the building was in front of a pond or a fountain. In the therapy group there was a handful of people, between 5-10 I suppose. Propably a bird or some other kind of pet too or the girl had one in her home. The man found this girl from the group, they started dating. The dating was difficult due the mental illnesses they both had. I don't remember if they moved in in some point. I do remember a scene where this girl escaped the man (because her feelings were hurt) to a unfinished building which was a special place for her. The man figured she would be there after he had searched for a while. I suppose there was happy ending after that. There might had been a scene where the man and the girl were there before and that's why the man knew where to look for her.

I am desperate to find out what is the name of the movie. I remember it being a good love film.

The Other Sister

The Other Sister (1999) - IMDb (http://www.imdb.com/title/tt0123209/)

No I'm sorry. It's not The Other Sister.

Is this an old movie possibly from the '70s?

No I don't think so. Probably between 1990 and 2000. I don't remember it being very old, but it wasn't new either.