There's no reason she can't have both Themyscira and a city all her own. Now, I like the idea of her having a city, but that's because I tend to think that the real superhero gold is when the ordinary meets the extraordinary. So, places like Themyscira, Atlantis, Asgard, etc. don't do much for me. The question is which city would be best for her. She's been in Washington D.C., Boston, Gateway City, New York and according to the DCEU Paris (probably more because I haven't read the comics in a while). Now, I'm partial to Gateway because that's where Cassie is from. However, some have expressed a dislike for the city changing from a St. Louis stand-in that the Spectre used to haunt to a fake San Francisco for Wonder Woman. It might be better to develop a new place with its own character.