"It'll affect my stamina during a race and will make it harder to finish in the top three," she said.
Her mother, Mandy Colman, said the thefts would seriously affect Maia's performance as they could not train at the track after school because it was too dark.
"Riding to and from school was just making sure she got the exercise in ... she's going to have to make up the exercise another way."
Maia had a racing bike for competitions, but was unable to ride this to school. The bike stolen last week was Ms Colman's, which Maia had been riding after her new bike was one of five stolen from the school in March. The thefts occurred while staff and students were at Frimley Park for swimming sports.
When her bike was stolen the first time, Ms Colman said her daughter had been in disbelief.
Thieves had broken the bike's padlock. This time Ms Colman said they removed timber struts from the bike rack's frame, taking them as well as the bike.
"It's not the school's fault, I just think the lock-up area needs to be more secure," she said. "I felt so silly because we didn't have the bike insured. We'd just moved from Australia and still had expenses over there."
A police spokeswoman said bikes could be highly valuable items, so they urged people to use common sense when leaving them in public places.
"Try to park your bike in a well-lit area and chain it securely to a bike rack or fence to help prevent opportunistic crime. Owners are also advised to keep a record of their bike's serial number," she said.
Hastings Intermediate principal Andrew Shortcliffe was unavailable for comment.