This is part of the Buffy: The High School Years comic book run by Dark Horse. Get it here on Amazon.
 
Buffy struggles to deal with her mom Joyce's newfound interest in spending time with her. Balancing that with her schoolwork, her friends, and her regular vampire-slaying duties is a challenge. However, when Joyce becomes hypnotized by a child-like demon that craves motherly care, Buffy experiences a new kind of sibling rivalry--except in Buffy's case, her "sibling" is actually a monster!