My Mom's a Werewolf (1989)

The frustrated housewife Leslie visits an animal shop to purchase a flea-collar. Unknowing that the owner is a werewolf, she accepts his invitation to lunch and later in his apartment. Through a bite in her toe he starts her slow transformation in a werewolf. Home again, she desperately tries to hide the often disgusting process from her family, but her daughter Jennifer and her - from horror magazines well educated - friend recognize what's going on, and help to kill the non-human.

https://www.youtube.com/watch?v=-WqHSFeHNUs