Because of her magic - Lady Tremaine wouldn't get anywhere near her

Lady Tremaine would be the win fight who locks Cinderella in her room. Two Steps sister argue and fight each other. But in fact i found Cinderella as the most boring Disney movie those are for the kids.

If we're talking about the original films alone, then Mim would obviously win, although if we're talking about sequels, where Tremaine has the wand, then you have an interesting fight. I think it would be close, because Mim is so tricky, but Tremaine is no holds bar and goes all out. She even tried to kill her own daughter. Mim is only interested in fighting for the fun of it, Tremaine would be in it to win it...

Outcome: Mim starts off with the clear advantage with her magic, running circles around Tremaine and her daughters; but being Madam Mim, rather than outright killing her opponents, prefers to have some fun and F** with them before doing them in. Tremaine is aware that Mim will be impossible to beat without magic and so she dispatches Anastasia to steal the Godmother's wand again while Mim is distracted by Lucifer, who she terrorizes by transforming into Maximus the Horse before going after Drizella in the form of a swamp rat.

During this period, Anastasia returns and from there, with the wand in Tremaine's possession sh** gets real, and Mim is forced into trying to hold her own in a serious no-holds bar "Wizard's Duel." Tremaine blinks Mim into the inside of a thorn covered pumpkin, turns herself into bacteria to inflict Mim, and matches her deadly animal transformations perfectly, making Merlin look like an amateur.

It looks like Tremaine will be taking the match until the Fairy Godmother shows up again, demanding that her wand be returned. As she begins struggling with Tremaine for possession of the wand, Mim proceeds to screech about how much she loves catfights and enters the scruffle while laughing hysterically, only briefly after Anastasia had joined the tug of war to help her mother. Unfortunately she makes the mistake of uttering the word "silly old garden gnome again," but this time, the magical blast doesn't exactly hit the Godmother.

Winner: Draw (both Mim and Tremaine have until the stroke of twelve until they turn from stone to humans again lol)