I will be moving to Fontenay aux Roses while my work is in Gif-sur-Yvette. I'll be using RER B daily and will be living alone. As a young female, I am a bit concerned for my safety. I would really appreciate it if you could point out places to avoid and if these areas are safe! Thanks!
It really depends on where exactly you live and what are your hours. If you come back home late at night and you live in the middle of what they call a "cité", then it might not be the safest place in the world at that time.
If you come back home during peak hours in RER B and you live in a house in the residential areas, then it should be ok.