Pam Burkhart

From Groovypedia, the "That '70s Show" Wiki

Pamela Burkhart (played by Brooke Shields) is the mother of Jackie Burkhart, with whom she has a very strenous relationship with. This mainly stems from trauma Pam exposed Jackie to, for example, by cheating on her father, (one of these affairs resulting in Jackie's irrational fear of clowns) and then by abandoning her family to run away to Mexico.

Pam seems to be also where Jackie has gotten much of her shallowness and vanity, and she is seen as a "neighborhood mom" to all the men in the series, causing constant tension between Pam and Donna and Kitty as well.

Later, Pam starts dating Bob.