Operation Daddy by Ava Sinclair

It’s the perfect opportunity for youthful-looking Detective Mia Coffman—going undercover as a teenager to find out who’s running a drug ring at Millsburg High.
The only hitch? Veteran detective Ramsey Holden will be posing as her father, and he insists they stay in character.
Despite Mia’s resistance to his method, Ramsey is firm. But he soon discovers that the roles feel more and more real as Mia’s challenging behaviors spark his naturally paternal nature.
When it’s apparent that Mia needs a real caring father figure, Ramsey finds himself assuming a private role in an effort to heal her wounded heart.
But there’s still work to be done, and Mia—who’s always lost everyone she’s ever trusted—finds her personal feelings conflicting with her professional goals in a way that could cost her dearly in what becomes a very dangerous operation.