I vaguely remember when I was about 10 years old seeing and episode of Samantha and Darren talking in the kitchen and Samantha said if I put a spell on mother and she finds out she will kill me. Was there ever an episode where Sam put a spell on Endora?

Episode # 199 "Turn on the Old Charm" from season 6 is the closest there was to Samantha ever putting a spell on Endora.

In that one Samantha used a magical amulet used over the century's by her Father to control Endora.

She Borrowed it from Maurice to control Endora & get her off of Darrin's back
, it worked for a while but let to Hysterical complications & Endora's subsequent retaliation, Brilliant Episode.

Larry Tate :)