When Liane Cartman was first created, she was apparently named after the ex-fiance of show creator Trey Parker, who had apparently cheated on him in their personal relationship. This is why the earlier seasons show Liane Cartman in such a demeaning manner. As the years have gone on, Liane’s more maternal side has been shown, which is apparently inspired by Parker’s own mother. Liane and Eric Cartman have had a sordid relationship to say the least, and this isn’t to say she hasn’t tried to combat his horrific personality.
In the season 10 episode “Tsst,” Liane finally admits that Cartman is out of control and seeks the help of reality TV nannies, but the only person who actually makes any impact is Cesar Millan, “The Dog Whisperer.” Unfortunately, after it seems like Cartman has changed for good, Liane immediately bends to his wants and desires when she realizes Cesar doesn’t actually want to be her friend, he was just doing a job by training her child.
Due to her negative reputation in the community, and the fact her son is consistently the most hated person in the town, Liane Cartman doesn’t have a lot of friends. She has developed a codependent relationship with her son, and she lets him get away with everything (including literal murder) because she’s clearly terrified of being alone. Cartman is all she has, and she’s willing to endure his endless barrage of mistreatment if it means someone, anyone in her life, loves her. But after 25 years of his crap, she’s done. Everyone has their limit, and Liane has finally found hers.