I have recommended her books before on this thread and after reading the third in the series I think she deserves her own thread. The series revolves around Kara Gillian who is a homicide detective who is also a summoner of demons.
Mark of The Demon
When Homicide Detective Kara Gillian finds traces of arcane power on a body, she quickly realizes that this is no ordinary murder. The serial killer known as the Symbol Man is a nightmare that Beaulac, Louisiana thought had ended three years ago, but now he's back for an encore and leaving every indication on the flesh of his victims that he is well-versed in demonic lore.
However, Kara is a Summoner of Demons, and may be the only cop on the city's small force who can stop the killer. Able to see and interact with a world most people can't, Kara must draw on her skills as a police officer and master of the arcane to stop the Symbol Man from killing again and possibly summoning something even she can't control.
But with a demonic lord of unearthly beauty and power haunting her dreams, and a handsome yet disapproving FBI agent dogging her waking footsteps, she may be in way over her head....
I thought the premise was different, and the main character is a woman who is strong, but has some vulnerabilities and personal insecurities.