Barbara was a classic whore. She originally dumped Dennis and Dee's biological father Bruce Mathis and married Frank because she thought Frank was richer than Bruce and because Bruce was more generous as he gave his money to charities. Bruce had in fact inherited a large fortune from his father when he died.
She was a cold, cruel, selfish woman with little affection for her husband or daughter. She seemed to favor Dennis over Dee. In her will she left Frank and Dee with nothing and stated that Dee was a mistake (despite the fact that Dennis and Dee are twins). She could be arguably considered to be one of the worst and most despicable human beings in the show.
She also expressed no concern for Dee after seeing her in a neck brace. 
Barbara died from a botched neck lift. ("Dennis and Dee's Mom Is Dead")
She was the daughter of Heinrich "Pop-Pop" Landgraf who outlives her.
Barbara was born in 1948. ("A Very Sunny Christmas")
Frank started a company with his partner, and stole all the money from his partner. ("A Very Sunny Christmas")
Barbara tricked Frank into raising the twins because she thought he was wealthier than their biological father, Bruce Mathis. ("Dennis and Dee Get a New Dad")
During this season, she reconnected with the twins, divorced Frank, and slept with Mac.
Frank tricks Dennis and Dee into revealing their mother's corpse to get revenge on Dee for stealing his money. This causes Dennis to feel emotions again. ("Charlie's Mom Has Cancer")
- Barbara's maiden name would be Barbara Landgraf, since we learn that Pop-Pop is her father, and his name is Heinrich Landgraf. ("Pop-Pop: The Final Solution")
- According to Frank, when Barbara was giving a birth to twins, the doctors were forced to do a C-section - because of Dee's giant hands. ("The Gang Reignites the Rivalry")
- Alternate title for 7th Season episode "Frank's Pretty Woman" says "Frank's New Whore Wife" - it's a straight hint to Barbara.
- According to Frank, initially Barbara was carrying triplets in her womb at the time, and the third one was supposed to be called Donnie, but Dennis and Dee "devoured him before he could be born". ("The Gang Gets Analyzed")
- Frank, Dee and Dennis weren't on Barbara's funeral. ("Charlie's Mom Has Cancer")
- Barbara's dog from 02x02 was named Bruiser, and it died in 2006. ("Charlie's Mom Has Cancer")
- Season One: Underage Drinking: A National Concern (mentioned only)
- Season Two: Charlie Gets Crippled (mentioned only), The Gang Goes Jihad, Mac Bangs Dennis' Mom, Dennis and Dee Get a New Dad
- Season Three: Dennis and Dee's Mom Is Dead (mentioned only)
- Season Five: The Gang Gives Frank an Intervention (mentioned only), The Gang Reignites the Rivalry (mentioned only), A Very Sunny Christmas (mentioned only)
- Season Seven: Frank's Pretty Woman (mentioned only), Frank Reynolds' Little Beauties (mentioned only)
- Season Eight: Pop-Pop: The Final Solution (mentioned only), The Gang Gets Analyzed (mentioned only), Charlie's Mom Has Cancer (as a dead body)
- Season Nine: The Gang Tries Desperately to Win an Award (mentioned only)