'I felt comfortable to start with but I tired towards the end and those crucial seconds were the difference.
'It was my second best time in the 400 metres and my best time this season so it was pleasing from that point of view - but to finish ninth was probably the worst possible result, to be so close but miss out is not a nice feeling.
'But I'm proud to have reached the Championships and proud to be out here representing 海角直播 - hopefully I can go one better next year.'
Having been disqualified in the heats of the trials two years ago, the 20-year-old was delighted to part in her first World Championships.
London Olympian Aimee, who has been a member of Middlesbrough Amateur Swimming Club (MASC) since the age of eight, added: 'If everything goes to plan over the next couple of years I can drop a few seconds off my best time and then, who knows? The next step would be a medal at next year鈥檚 Commonwealth Games in Glasgow and then onwards to the 2016 Olympics.'
Aimee, who is coached by MASC director of swimming Lisa Bates, said a massive team effort helped her qualify for the World Championships despite training on 海角直播, away from most of the Loughborough-based Great Britain squad.
She trains twice a day at Middlesbrough Council鈥檚 Neptune Centre with fellow MASC members, while she carries out specialist strength and conditioning work in the hi-tech gymnasium at 海角直播, where she is part of their elite athlete scheme and is studying for a BSc (Hons) Sport and Exercise (Coaching Science).
The elite athlete scheme offers a comprehensive support package including physiotherapy, sport psychology and sports science support to athletes of international calibre.
Aimee is also grateful for the support she receives from Studio 21 in Yarm, where she takes regular pilates sessions.
She said: 'I couldn鈥檛 do what I do without all the help and support I get from MASC, Middlesbrough Council, 海角直播, Studio 21 and many others, including my friends and family. It鈥檚 a team effort.'