White Witch

Ray is the fae ambassador to the human city of Haven. Haven is a place where humans can interact with the various creatures of Faerie, another realm whose inhabitants remained hidden from humans until "the lifting of the veil." Haven is not only a place where the fae can visit earth, but is also home to vampires, demi-demons, faelings, and other hybrid creatures, along with human witches. Ray is herself a hybrid, but a forbidden hybrid between a Seelie fae and a demon–none other than the King of the Hells himself. Faerie's cruel Queen has forbidden dilution of "pure" Seelie fae blood by mixing with "lesser" races, especially demons, with whom Faerie has an uneasy truce following a bitter war.

Ray's position as the fae ambassador is valuable in that it gets her out from directly under the thumb of the Queen, who enjoys tormenting Ray because of her heritage but keeps her alive for leverage against the King of the Hells. Ray's position also means she cannot have contact with her demon family. 

Aside from her ambassador duties, Ray runs a private detective agency. This side job allows her to skirt the law and even the Accords which govern relations between races when need be. However, it also causes her an enormous headache when the white witch, Lily Storm, goes missing, because it forces Ray to choose between loyalty to her family or her Queen. Lily, it turns out, is mated to one of Ray's demon cousins–and demons mate for life.

Taking a job for her father searching for a missing witch is bad enough, but Ray's father has other plans for her which could place Ray into direct conflict with the Queen if they are discovered–placing Ray in danger of death or worse.
As Ray hunts through various suspects in an effort to find the missing white witch and keep her position as fae ambassador, she realizes that more fae and faelings are going missing and it all might be connected. But with tensions between demons and fae so fragile, it's up to Ray to figure out what is going on and return the witch to her demon cousin while saving the others.
If you enjoy 'White Witch' Book 1 then check out book 2 'Where art thou?'