Sandra Bullock is talkin' some serious smack about Jesse James' ex-wife ... according to new legal docs.
Jesse's ex, Janine Lindemulder, claims she was driving with daughter Sunny recently when the kid accused her of being a liar.
The conversation started innocently enough -- when Janine was explaining to Sunny it was wrong to lie.
According to the docs, filed in O.C. Superior Court, Sunny blurted out, "Sandy said that you lied to the police and that's why you went to jail."
This isn't the first time Janine has claimed Sandra bad-mouthed her in front of Sunny ... as TMZ first reported, Janine alleges Sandra said within earshot of Sunny, "Quite frankly, I'm glad Janine is in jail. She can go ruin someone