What happened to veronica mars' mom?

Answer 1

In season one Veronica tells her to leave after finding out that she has not quit drinking. Her mother steals a 50,000 dollar check from Veronica and her Dad before she leaves. She is not mentioned in the subsequent seasons.

Answer 2

Originally Veronica's Mother; Lianne had left because of the public backlash that resulted in her husband being expelled as the local Sheriff, she later returns and her daughter Veronica decides to help her out with entering a rehab factility for her alcohol addiction however Lianna checked herself out of the rehab and continues to drink and is forced out of Veronica's life but not before she steals the money that her ex-husband Keith was awarded.

Answer 3

She was threatened by Celeste Kane, because her mother had an affair with Jake Kane, and was not sure who Veronica's biological father was.