The Strangers on Montagu Street by Karen White (Tradd Street, book 3)

Psychic realtor Melanie Middleton returns-only to be greeted by a house full of lost souls.  

Psychic realtor Melanie Middleton is still restoring her Charleston house and doesn't expect to have a new houseguest, a teen girl named Nola. But the girl didn't come alone, and the spirits that accompanied Nola don't seem willing to leave...