Bīderu no Haha
Videl's mother is the ex-wife of Mr. Satan and the mother of Videl. She is never seen in the anime or manga. She is deceased according to the Daizenshuu. Since her absence, Mr. Satan started hanging out with a lot of women.
It is hinted in Dragon Ball Z that she could have left the family when Videl states to her father, "Just because mom left, it doesn't mean you can start hanging around all these other women!".