The only thing I would add is that I think Mademoiselle Rouge should use this opportunity to tell her friend that it bothers her that her friend isn't more interested in her family life, and subjects like her friend's boyfriend and talking about the future with one another should also be a part of their friendship, if their friendship is to grow and last for years and years.
H'mm. Maybe, maybe not.
You can't force someone to share your interests. It may bother Mademoiselle Rouge that her friend doesn't find those topics interesting but it's not her friend's fault.
They have different relationships and different lifestyles, if conversation is concentrated on the parts that overlap then there's not a worry that someone is feeling left out or made uncomfortable.
By all means the subject can be broached and shouldn't be deliberately avoided as certain things are bound to come up in the every day details but then it also shouldn't be forced either or it's going to become a much bigger point of contention.
If they're never going to be super best friends that tell each other everything and spend a lot of time together, there's not a need for the kind of closeness where you can talk freely about absolutely anything and everything.
I think most people have friends that fit with different aspects of their lives, I've got work friends, internet friends, old school friends, a truly best friend and some casual people who drift in and out of my life to say hello now and again. I know my work friends would feign polite interest but eventually, they'd end up staring at me blankly and change topic if I started blathering about computer components and video games. Same goes for my internet friends if I were to talk to them about Key Stage 3 lesson planning and behavioral management.
Cinderella-ish but in this case, I'd say probably better to leave things and try not to put feet in a shoe that doesn't fit.