Grammatically, the possessive adjective (son/sa/ses) may be either "his" or "her". But what the grammar does not tell you is that it will be understood as referring to the subject of the sentence. Here are a few examples:
- Il est tombé de son cheval = he fell off his horse
- Il est tombé de son cheval à elle = he fell off her horse
- Elle est tombée de son cheval = she fell off her horse
- Elle est tombée de son cheval à lui = she fell off his horse
Not that I know of, and I'm not sure that we really make such a distinction in English either. The distinction you mention doesn't strike me as one people actually make in spontaneous speech/writing, i.e. it sounds like an academic distinction without much to support it. If you look up "seldom" the definition is "rarely" and if you look of "rarely" the definition is "seldom".