The seven-times European junior individual and team champion, 23, fell from her horse Tis A Beauty while competing at Tweseldown Racecourse in Hampshire a week ago.
She was kept under sedation following the accident to help her lungs recover from injuries "consistent with being crushed" after brain tests came back clear.
"Progress people... I have been for a walk down the corridor!" she tweeted on Monday.
"My face is covered in some beautiful bruises but all in all I'm good!"
Collett has been dressage training two-times Cheltenham Gold Cup champion Kauto Star in recent months.
Collett rose to prominence through show pony riding before switching to eventing and becoming one of Europe's top young riders.
She has since made the step up to the senior squad, competing at the 2011 European Championships, and while she did not make the Olympic team she had been expected to feature prominently for GB over the next few years, including at Rio 2014.
Tis A Beauty was unharmed in the fall.