Elizabeth "Betty" Giselle-Deville is Phil and Lil's mother and also the wife of Howard. She is very nice, but also tends to speak in a strong voice. Even though they outwardly seem to be opposites, Betty and Didi are very good friends. She comes off as a tough and energetic woman, always giving a friendly-but-painful back slap, and fawns over her twins. She loves a good cup of coffee and is always quick with a witty comment. The character seems to be into sports (as she used to be a pro-wrestler) and always wears a blue headband. She is voiced by Kath Soucie, who also voices Belinda, Phil, and Lil.
Despite being a tomboy, Betty considers herself a feminist, and wears a purple shirt with the symbol for "female" on it. Her big brother, Freddie, wears a shirt identical to hers but has the male symbol on it instead. In All Grown Up!, she works with Chas at the Java Lava Coffee House, and also helps Principal Pangborn with the school's soccer team, which Phil and Lil are a part of. Despite their age difference, Betty really loves Howard. Betty met Howard when she finished college in 1982, and she immediately started dating him. They got married in 1987, right after Stu and Didi's wedding, and they renewed their vows in "Runaround Susie".
Betty has peach skin, brown hair, pink lips and a pair of white eyes with black pupils. She wears green earrings, a purple-and-orange shirt with the female symbol on it, blue jeans, orange socks, blue and green sneakers and a blue headband. She has a very large build.
Betty has appeared in many episodes of Rugrats and All Grown Up!. Her first appearance was in Tommy Pickles and the Great White Thing. She goes on to make even more recurring appearances in the spin-off series All Grown Up!, running the coffee house with Chas.
- In the episode Mother's Day, it is revealed that she used to breastfeed Phil and Lil when they were under a year old, though, being that it aired on Nick, it could not explicitly be shown (i.e her shirt wasn't lifted).
- In the All Grown Up! episode TP+KF, she is shown to be a Halloween prankster, and disapproves of no fun.
- Betty was born in 1959, but she's older than Didi.