Some TMNT stuff really isn't for little kids.
Dr. Libby Meitner, nicknamed "The Inventor" by Darius Dun and the Street Phantoms, is a scientific engineer and the former partner (and separated wife) of Harold Lilja. She has been pressed into service by Dun to create devices that will allow him and the Street Phantoms to overtake New York City.
She was also central to Dun's attempts to win Lilja into working for him as well. With no choice in the matter, Libby did her best to convince her ex-husband of her desire to reunite with him, despite his enduring mistrust of her. When the Foot Clan invaded Dun's stronghold, Libby turned against Dun in order to protect her ex-husband. In the process, she suffered severe injuries when a Street Phantom attempted to kill Harold.
When Dun was conquered and executed by Splinter's Foot Clan, Meitner fled with Lilja, reconciled their differences and started living together again. She was seen to be in a wheelchair at Christmas, and some months later was walking again with a crutch.
After Harold reconciled with Donatello, she joined them in souping up the Turtle Van.