Tabby doesn't know kung fu per se. She improvises like MacGuyver.
She was instructed a little in martial arts by her mother and some friends, but never went beyond a yellow or red belt in karate. She's no black belt.
Tabby's idol, Candi Flippo / Ciem, was predestined by a genetic experiment on her father to have centipede-themed abilities, making her pretty much an analog of Spider-Girl. Candi was also trained in martial arts, and used her centipede abilities to advance herself intuitively. So Candi is like Spider-Girl with a bit of Black Widow in terms of fighting style. Tabby has nowhere near that skill level with martial arts per se. She's an intuitive fighter, and can improvise well, but is not a professionally trained nor a particularly disciplined martial artist.
She has learned from watching Ciem fight as well, and has learned a lot of life facts from her mother and from the Gray Champion. Other than that, whatever else Tabby learned, she learned on the streets as she went along with Sarah as a tutor. That, or she learned it at Mansfield Juvenile Treatment Center from the other inmates she was with.
Candi had been to Madison Juvenile in Indiana 11 years prior to Tabby being sent to Mansfield in late 2026. Candi taught Tabby prison slang, just in case the government ever betrayed the Sodality Church / Sodality of Gerosha which both girls had become a part of by 2021. (Which, the government eventually did betray them, after Rappaccini's plants started getting their way.)
So other than what she learned from a handful of superheroes, none of which truly committed themselves to teaching her, Tabby acquired most of her skills in prison. Tabby often proved the wiser tactician of the two girls, and the better negotiator, and to have better morals. Sarah, however, was the expert on how stuff worked. Occasionally, the girls would teach another inmate some of their knowledge, and would be taught skills in return. Behind the staff's back, they made it "MacGuyver School."
Tabby and your gal sound like they could, under the right circumstances, be dangerous to each other. If the girls ever teamed up, they'd pose an even greater danger to the Chrome Kite and Icy Finger than either alone.
Tabby only accepted the offer to take away Marge's power and distribute it amongst her friends for one reason: because it would be them and their courier / spy ops versus an entire cabal of baddies that had exiled the legitimate government and taken over the state - a cabal of supervillains that had its own army to send after Tabby and her friends. And even if they didn't face the newest incarnation of Stagtar or Microwave Mouth that week, it didn't matter: helicopters and bullets are not funny. And even if the police chief sympathizes with you, he still has orders to shoot on sight.
In other words, she only got superpowers because she can't afford to go down from a single bullet. She needs to be tougher. Otherwise, she would not have even agreed to have powers. It violates the code of the Keepers of Hester's Locket, a code which warns against using Marlquaanite rubies and bonds for personal gain.