This question already has an answer here:
It's been many years since I had French, so I am in doubt about a very basic thing. Let's say you want to say her school. école is feminine, so you'd expect sa, and thus s'. However, Google Translate seems to make each feminine word starting with a vowel masculine when using a possessive. It returns son école. When trying to translate that school, though, it correctly translates to cette école.
So is this a bug in Google Translate, or is it indeed the case that sa + feminine-starting-with-vowel becomes son feminine-starting-with-vowel? It feels unnatural to use son for me.