Tear her apart? Nah. I'd make sure she's very well treated somewhere very far away from Varric. Imprisoned yes, but with all of her needs being attended to, and no mistreatment whatsoever. The guards would have to be gay men in order to resist her charms.
Then, after Varric falls in love with me and marries me, she's free to go. If this takes years, then so be it. I will continue to treat her well until he's mine. If she comes near Varric, I'll kill her on sight. It's nothing personal, but I wouldn't trust a fellow rogue in this case. She does have Carta connections after all, but there are places even the Carta doesn't know about.
As long as she's a good girl, she has nothing to fear.
Really, you guys are lacking in the creativity department. 