Trickett failed to qualify for the 100 butterfly earlier in the trials, putting paid to her hopes of defending her Olympic title, but her top-six finish in the freestyle ensured she will be part of the Olympic squad and will be considered for selection in the relay team in London.
"I'm speechless because it's amazing to see where I've come in the last two years," said the 27-year-old eight-times world champion, who returned to the pool in September 2010 after a short retirement.
"It's exciting for our relay this year. That sort of depth is really going to put the world under the pump."
Melanie Schlanger won the title in 53.91 seconds to qualify for the individual event at London along with runner-up Cate Campbell.
Seven-times world champion Michael Klim's London ambitions ended abruptly when he failed to make the final of the 100 butterfly after swimming 14th fastest in the semi-finals.
The 34-year-old had hoped to make his fourth Olympics after announcing his comeback last year following four years out of the pool. He promptly announced his second retirement.
"That was the last turn, I think," said Klim, who won two relay golds at the Sydney 2000 Games.
"I might do the relay on the last night but that's pretty much it... Back to changing nappies and back to work."
Klim's great rival Geoff Huegill was fifth fastest into the final behind pace-setter Chris Wright. The 33-year-old Huegill, twice a world champion, is bidding to qualify for his third Olympics after returning to the pool following a high-profile battle with weight problems and depression.
World champion James Magnussen, who won the 100 freestyle title on Monday in a scintillating 47.10 seconds, qualified fastest into the 50 freestyle final ahead of Olympic silver medallist Eamon Sullivan.
Triple Olympic champion Leisel Jones, who will defend her 100 breaststroke title in London, missed out on qualifying in the 200 when she finished fourth in the final won by 18-year-old surprise packet Tessa Wallace.