Interesting question you pose do they go vintage or modern?
I think a modern City theme specifically geared toward girls is a great way to go. I know I struggle to find sets for my daughter that are not too "girly" as she has outgrown princess stuff. Fortunately, she likes Star Wars so some of those sets she enjoys. Recently I got her the Camper set and Small Car.
Personally, I think the Creator series has some great sets that girls could enjoy. I plan to give her the Beach House and Apple Tree House that I got off ebay recently. I also plan to give her plenty of girl mini figs to go with them. This is for an end of school year good grades reward.
Some good City themed sets I think would work for girls based on what my daughter enjoys:
Horse Ranch
Concert Hall with a pop singer and a band
Fashion Boutique
Pet Shop (glad to see that set has been made, but maybe a more moderately priced one would be even better)
Dog Park or simply a City Park (could have bikes, scooters, etc)
Artist or maybe Ballet Studio
School House
Cruise Ship scene
Doctor's Office
Vet Office
Hair Salon
I don't think these sets have to go overboard with the pastels to appeal to girls. They just have to be of subjects girls would enjoy playing with. These sets could work with the existing City theme as well.
I'm sure there are even more great ideas.