Absolutely! There's a bunch of prostate massagers I've wishlisted just for the purpose of vaginal use! Lol. I've never been brave enough to buy one yet because I'm afraid it just won't work, but I've been desperate to try one of Nexus' toys for G-spotting! The only reason I've stopped myself from doing so is because they're very high for what they are.
Go for it! The only real difference with guys toys is that they have a base to prevent them from getting stuck in the rectum. The G-spot is positioned much the same as the P-spot so both kinds of toys share a lot of the same shape and function.
No reason not to heck a lot of time companies will take the same toy paint it two colors and call them two separate toys, one market to men and the p-spot one to women and the G-spot. That should tell you how similar they can be.