Realm of Kings by KC Kingmaker

I did not come to Camelot to choose, yet I now face the most impossible choice of all…
I hold a secret no one else knows. A secret that will change the entire landscape of Logres. Merlin said it’s for my ears only—that if I tell King Arthur, it will disrupt the mythical prophecy.
But screw the prophecy, right? I’m not sure how long my chatty ass can hold onto a secret of this magnitude anyway.
I have to choose Camelot or my own world. To end the cycle trapping this land in a vicious time loop, I can never leave. If I do leave, I can never return. I have to be stronger and braver than my ancestors, who failed to stop it. I don’t want to live in Camelot without Arthur and my sinful Knights of the Round Table, but I can’t imagine living in my world having known them, either.
My knights are obsessed with me. They see me as their Ever Queen, with untapped power . . . and the weird shit I’m starting to do might prove them right. They think I’m the key to stopping King Mordred’s reign and the terrible curse cast by Morgan le Fay. For all our sakes, I can’t let them down.
It’s time for war.