Technically I guess she could have. But Sango and Miroku would have died a long time ago and the demons would have aged quite a bit if they had survived at all, since there are no demons in Kagome's time. For example, it took Inuyasha around 200 years to age 15 human years (Rumiko Takahashi gives this number in her Inuyasha profiles book) so in 500 years he may be in his fourties. Kagome would have to wait a very long time to be with him, as 18 year olds don't really date middle aged men. Rumiko Takahashi just wanted what would make her the happiest and choose for Kagome to live with the ones she grew to love in the Feudal Era.