About 15-20 years ago I have seen a film (together with my aunt and grandfather, but I asked them last week and they couldn’t remember it) with the following elements:
– main characters were nun and a man (I think he was an ordinary man, not a priest); I couldn’t find it in this list: https://en.wikipedia.org/wiki/Category:Films_about_Catholic_nuns
– the nun is very ill (possibly tuberculosis) and dies at the end of the film; it is not “The Song of Bernadette” or “The Bells of St. Mary’s”
– I am quite sure it was shot in colour, but I leave small chance that I am misremembering this
– there were some scenes shot outside of the monastery/convent and the man and the nun were talking a lot about a certain plant (I THINK it was “heather”, but I have seen it subtitled in my language, and I didn’t speak any English at the time)