April Reeves died after the collision on the A371 between RAF Locking and the Helicopter Museum, near Weston-super-Mare, at about 15:00 BST on Thursday.
Avon and Somerset Police said she had been cycling with her mother and 10-year-old brother at the time.
Her family said they are all "completely devastated by her death".
Police are appealing for any witnesses to contact them.
A seven-year-old cyclist who died following a crash with a car in North Somerset was "greatly loved" her family has said.