That's basically it. Gabrielle Delacour is 11 years old when she arrives at the Burrow with her parents for her sister's wedding three years later:
“And, of course, you ’ave met my leetle daughter, Gabrielle!” said Monsieur Delacour. Gabrielle was Fleur in miniature; eleven years old, with waist-length hair of pure, silvery blonde, she gave Mrs. Weasley a dazzling smile and hugged her, then threw Harry a glowing look, batting her eyelashes. Ginny cleared her throat loudly.
Harry Potter and the Deathly Hallows, Ch.6 "The Ghoul in Pyjamas"
So why does the movie version take an eight year old along for a trip to a foreign school when she shouldn't even be attending Beauxbatons yet!
I am aware that the probable out of universe reason is to establish closeness to her sister, so that the viewer cares she is rescued during the second task, but what in universe (if any) reason did the screen writer or anybody from production give for her presence? Was Gabrielle supposed to be older in the movie (her actress, born in '92 certainly was).