Johnstone, 26, from Southwick, has just returned to action after she snapped the cruciate ligament in a knee and was out of action for a year.
She is now back competing in competitions and wants to prove to the selectors that she deserves a place in the squad.
She said: “I was out injured for a year after I was injured at a training camp in Japan. It was just a flukey throw.
“I’ve been in judo a long time and just screamed out when I went down. I’d never experienced pain like it before, so knew it wasn’t good.
“But, I was lucky enough to have the operation done by one of the top British surgeons, who also did Freddie Flintoff’s knee.
“It was really frustrating as I missed out on the European and World Championships.
“But I’m so grateful that it happened when it did. If it had been a year later, it would have been too late for me to come back for the Olympics.
“I’m now building up gradually and I recently had my first couple of competitions back.
“I had a local one, where I won gold, and then got gold again at St Helens, which was quite pleasing as I beat a couple of good people.
“I then won gold at the Swiss Open in Geneva the weekend before last, winning five fights against some top players from France, Switzerland, Lithuania and Germany. I was really happy as this was my first International competition for 16 months because of my knee injury and, hopefully, it is a good stepping stone towards London 2012.
“I’ve been quite busy but it’s great to be back competing.”
Getting to the Olympics has been Johnstone’s goal for several years. She competes in the under-52k category and is a second dan black belt and is the No 1 in Britain in her weight category.
She won a silver medal at the National Championships aged 12 and a place on the Great Britain under-17 team and has progressed onto the under-20 and senior teams, retaining her place every year on the national team.
She said: “I’ve been doing the sport since I was seven and it’s always been my dream.
“To compete at the Olympic Games, in London, is a once-in-a-lifetime opportunity.
“I’m giving it everything to get there and, hopefully, I’ll win a medal.”
Johnstone, who was a Commonwealth champion in 2004 and won a silver medal in the GB World Cup in 2008 and a bronze medal in the same event in 2009, is looking for sponsors to help her compete in various competitions and go to training camps in the build-up to the Olympics, which cost in the region of £200-250 for each trip.
Anyone interested can e-mail her at [email protected]