I think rather than specifically showing her kids films you could show her innocent, adult films (like old fashioned black and white films). That's what my mum did with me when I was little and I think it prevented her from going crazy :D I've always appreciated classic films now because of it.
The Day The Earth Stood Still (1951) -- an alien comes to earth and tries to get people to be more peaceful. Early science fiction, it's great.
The Devil and Miss Jones (1941) -- the owner of a big department store poses as an employee and is shocked by how nice the staff are to him. Very sweet.
Bachelor Mother (1939) -- a single lady finds a baby on a doorstep and brings it to an orphanage. They believe she's the mother so she keeps it. Super cute!
Top Hat (1935) -- Ginger Rogers and Fred Astaire. He follows her around but she thinks he's married and keeps turning him down!
The Gay Divorcee (1934) -- Ginger Rogers and Fred Astaire again. He is a dancer but she mistakes him for an agent helping her to divorce her husband! The best Astaire/Rogers film imo.
Rebecca of Sunnybrook Farm (1938) -- Shirley Temple is taken in by her Aunt and is chosen to be the voice of Crackly Grainflakes on the radio, but her Aunt mustn't know!
Gentlemen Prefer Blondes (1953) -- Marilyn Monroe has to prove she's not after her fiancé's money by being loyal to him on a cruise.
Teacher's Pet (1958) -- a reporter pretends to be a student at a journalism class but feels guilty when he is given so much praise for his "natural talent".
Calamity Jane (1953) -- Doris Day is a feisty tomboy who is given a makeover but doesn't lose her personality.
The Love Bug (1968) -- a little car comes to life and wins lots of races for his racing driver owner!
The Ugly Dachschund (1966) -- a man rescues a Great Dane puppy and sneaks him into his wife's dog's puppy litter. Unfortunately the other puppies are dachshunds so he is foiled early on!
That Darn Cat! (1965 version) -- a cat helps the FBI to solve a kidnapping case! My favourite!
More recent films:
Barbie Rapunzel -- Barbie version of Rapunzel story.
Hannah Montana The Movie -- Milly Cyrus puts on a wig and no one recognises her so she is able to be incognito as a famous singer.
Spy Kids 1 & 2 (haven't seen 3 or 4) -- a brother and sister duo take on a spy mission when their spy parents get captured.
Sabrina Down Under -- Sabrina The Teenage Witch goes to Australia and turns a merman into a human.
The Parent Trap 1, 2, 3 and 4! -- Twin and triplet swapping.
Hope this helps, I've got loads more suggestions if you'd like any similar sort of films to the ones I suggested!