Gidget

Frances Lawrence (Sandra Dee) is about to turn 17 years old and is on her summer break between her junior and senior years of high school. She resists the pressure to go "manhunting" with her girlfriends and laments the days when the girls had fun together without boys. Frances also rejects her parents wishing to fix her up on a date with the son of a friend of the family, Jeffrey Matthews.
On a jaunt to the beach with her bikini-clad girlfriends, flat-chested tomboy Frances meets surfer Moondoggie (James Darren). She quickly becomes infatuated with him, but he shows no romantic interest, however Frances is more attracted to surfing than man hunting.
At home, Francie importunes her parents for $25 for a used surfboard. Russ and Dorothy Lawrence (Arthur O'Connell and Mary LaRoche) grant their daughter's request as an early birthday present and the excited youngster returns to the beach to surf. The gang dubs their female associate "Gidget", a portmanteau word based on 'girl' and 'midget'.
She associates with an all-male surfer gang led by the worldly beach bum, The Kahuna (Cliff Robertson). Kahuna is a Korean War Air Force veteran twice the age of Frances who was fed up with all the rules he had to live by when he flew combat missions and dropped out of normal society. He travels the hemisphere surfing with his pet bird. Moondoggie admires Kahuna and wants to emulate him by joining Kahuna in working his way on a freighter to go surfing in Peru at summer's end instead of going off to university as his self-made father planned. Kahuna and Gidget enjoy each other's company with Gidget questioning how he can survive an aimless and lonely existence without a job. She questions whether if Kahuna knew then what he knew now would he still make the same lifestyle choice after leaving the Air Force. Kahuna later reflects on Gidget's words after the death of his only friend, the pet bird.
Hoping to make Moondoggie jealous, Gidget hires one of the other surfers in the gang to be her date to a luau party on the beach. Her plan backfires when the surfer she hired pawns the job off on none other than Moondoggie, unaware that he was the one Gidget wanted to make jealous. Gidget lies and tells Moondoggie that it is Kahuna that she wants to make jealous, and they have a romantic evening at the luau. Eventually Moondoggie says something that upsets Gidget and, as she flees the luau, she runs into Kahuna and agrees to take him to a nearby beach house. Alone with Kahuna, Gidget tries to make Kahuna take her virginity. Amused, Kahuna attempts to call Gidget's bluff by pretending to take her up on her offer but finds himself falling under her spell. Realizing what he was about to do and angry at the situation he's been put in, Kahuna throws her out of the beach house just as Moondoggie arrives. Gidget is mortified and escapes out the back of the beach house as Moondoggie confronts Kahuna. The cops are called to break up the fight between Kahuna and Moondoggie and, after leaving the beach house, they find Gidget stranded with a flat tire and without her driver's license. They bring her in to the police station. Gidget's father, having heard about the incident decides to take over control of her social life, and orders her not to see the surfer gang again. She falls into a depression, to which mother shows her a tapestry from her grandmother reading "A Real Woman brings out the best in a Man".
In the end, Mr. Lawrence arranges a date for Gidget with Jeffrey Matthews that Frances grudgingly accepts. To her surprise, Matthews turns out to be Moondoggie. The two return to the beach to find Kahuna tearing down his beach shack and find out that he's taken a job as an airline pilot. Moondoggie and Gidget realize how they feel about each other and, as an act of romantic devotion, Moondoggie asks Gidget to wear his class pin. Kahuna cheerfully warns Moondoggie that Gidget is quite a woman.

Question: How old will Frances be?
Answer: 17 years old.