Forbidden Rose by Kathy Haan

I always said I wanted to grow up to be just like my mother—a small army of mates at my side, and more power than I know what to do with. But now that I’m facing the decision to upend everything we’ve worked so hard for, I’m caught at the crossroads between fate and free will.
To be with my soul bonded mate, I must ascend, and so must the rest of my mates. The risk? If it doesn’t kill us, it could sever our bonds for good. So we do what we must: plan to spend the summer strengthening our bonds and learning everything there is to know about magic, so we all make it through ascension in one piece and with each of our bonds intact.

But when magic itself starts to destabilize, we’re racing against time, and only our ascension can save it.