Necromancer. Coven, #11

Their greatest wish might be too good to be true. Samantha and Kathy are surprised to discover their mother, Marie, at their front door one morning. Especially since their mother died fifteen years ago. But the reunion is bittersweet. Not only is Marie evading questions about how she was suddenly raised from the dead, but innocent, healthy, young people are dying left and right the longer that Marie is in town.
Fearing the worst, the sisters try to simply enjoy the time with their mother. But Marie has a secret. One that could put the whole family at risk. Necromancer is the eleventh book in the Coven series, which is part of the Art of Magic universe, containing the Lost By Magic and the Under the Moon series.