Also, Born Yesterday. Judy Holliday as the initially bubble-brained mistress of a corrupt tycoon who hires a tutor (William Holden) to teach her some culture and manners when he brings her to Washington, DC. This is one of supervenusfreak’s favorite classic movies.
Labyrinth
The Man Who Shot Liberty Valence
You, yourself, might even enjoy it despite the fact that it’s a western. I detest most westerns and I think it’s one of the best films ever made. YMMV, of course. 
The Last Unicorn
Nausicaa of the Valley of the Wind
I’ll go by what my kid’s have seen and love
Both Boys between 7 and 9
Duck Soup (They love the line “He may look and sound like an idiot but don’t let that fool you he really is an idiot”)
Night at the opera
Day at the Races
Monkey business
Frankenstien (BRIDE OF … SONE OF… GHOST OF… HOUSE OF… VS WOLFMAN)
Dracula (a little too boring)
Wolfman
The Mummy
the Adventures of Robinhood
Men In Black (3 Stooges)
Disorder in the court
Sing a song of sixpants
All but a select few of the Our Gang Talkies
Phantom of the Opera
The Man who laughs
King of the Rocket men
Superman Vs the Mole men
Superman the Serial
Batman and Robin (1948)
Batman (1966)
Mary Poppins
Wizard of Oz
Willy Wonka and the Chocolat factory
The Kid
Modern Times
The Circus
City Lights
The Great Dictator
Those spring to mind immediately
Once I read the age of the girl in question, this was my first and strongest thought, but I was frankly a bit afraid and embarassed to even mention it.
But you said it first, so I’ll second it! It’s not a great or classic movie that will go down in history, but dammit, it’s still good. There’s so much harshly realistic portrayal of how young girls feel and act and think that’s it’s kind of depressing, but the truth in it manages at the same time to be hilarious.
Maybe too obvious? My favorite movies that feature teenagers/late adolescents, and/or strong women:
*The Breakfast Club
Over the Edge
My Bodyguard
Pretty in Pink
Little Darlings
Mermaids
Breaking Away
Parenthood
Ordinary People
Chariots of Fire
Stand and Deliver
Fried Green Tomatoes
Silkwood
Norma Rae
Real Women Have Curves
West Side Story
Fame
Wonder Boys
What’s Eating Gilbert Grape?
War Games
Election
The Great Santini
Sid and Nancy
Harold and Maude
*and of course
Fast Times at Ridgemont High
fessie, everything I’ve heard about the movie Silkwood does support your claim that it has some excellent strong female characters.
But I still cringe when I hear that title. If I could have the days of time I’ve wasted trying to explain to people that the decon methods shown in that film are pure Hollywood, I’d be about a month younger. It may be an excellent drama, and even a damning indictment of the nuclear power industry - but its science for at least one visceral scene is completely FUBAR.
In short, if it gets shown, please, please, please preface the move with a statement that that the personnel decontamination methods shown in that movie are pure Hollywood, and not a reflection of reality.
So you watch that, like, every Saturday? 
How about Cyrano de Bergerac (Mel Ferrer version)? Or Rear Window?
Sorry, I have to agree with her. I don’t think I had ever cried harder at a movie. 
How Green Was My Valley
The African Queen
Guess Who’s Coming To Dinner
The Yearling
I’ll second To Kill A Mockingbird too. Even my 7 year old has gotten tremendous mileage out of that one, layers and layers of lessons there.
I’m a little surprised that no one has mentioned Annie. That was a staple in my house, although that might have had something to do with my three red-headed sisters.
I’d also throw in something Marx Brothers just so she has a general understanding of their shtick. Pick a favorite if you have one, Duck Soup if you don’t.