The City of Portsmouth athlete, from Southsea, is joined by her club-mate and training partner Serena Vincent in the team for the prestigious event.
Both throwers are coached by Bronwin Carter and are among 72 young athletes, aged 14 to 18, who will represent Team England.
A host of future stars will be heading to the Caribbean from July 19 to 23.
Both City of Portsmouth athletes have been in excellent form this season and performed well under pressure to book their places on the plane.
Gaia has had to battle some major injury problems but has shown great dedication and determination and has now been rewarded.
She said: ‘It’s great to have us both going together. I know our coach is very proud of us both, this is definitely the biggest competition I have participated in so far in my athletics career.
‘I was really unsure about how my season was going to go, struggling with the knee surgery in the winter and a few niggles at the beginning of the season.
‘But I’ve worked hard and managed to overcome them.
‘I am delighted to be on the team going to the Bahamas, because although I have been to a couple of internationals, this will be my first time competing for England abroad.’
Gaia has been in Finland doing javelin training in recent days.
She’ll then start to get ready for her experience in the Bahamas.
‘It’s going to be such a great experience and I will be training hard for the next few weeks before we fly out,’ she added.
‘In regards to Finland, I’ve been working with a group of athletes from the club and other clubs in Hampshire.
‘We will be competing against and training among athletes from all over the world and under the guidance of some of the best coaches in the country and the history of javelin.
‘It’s a great experience and I’ve had a very enjoyable time.
‘Hopefully my time in Finland will be very useful in improving my javelin throwing.’
Serena is the under-17 national champion for shot put both indoors and outdoors.
She is also Hampshire and Hampshire Schools champion.
Gaia is national shot put under-20 champion and won both south of England indoor and south of England outdoor titles.
The 2017 Bahamas Games will feature up to 1,300 athletes who will compete across nine sports including boxing, tennis, judo and swimming.
Jessica Ennis-Hill, Beth Tweddle and James de Gale previously represented England at the youth games.