Loughborough University-based Nocher posted a time of 2 minutes 11.83 seconds in the morning heats which gave the 22 year-old a place in the finals and a degree of hope for posting an Olympic qualification time.
Nocher, who swam at the Beijing Games when she was sent on a B standard time, had to break the A standard of 2:10.84.
However, Nocher was a second off the time required at the halfway mark in the final and eventually finished in 2:12.74, leaving her struggling to get to London with only the Europeans to come in May as her final qualifying meet.
Earlier in the day, Gráinne Murphy, who has qualified for London, was the second fastest qualifier into her favoured event, the 800m freestyle, in a time of 8:32.85, the fastest time the 18-year-old had posted in the last two years.
The time puts Murphy into the top 10 on world rankings for the event and was second only to Britain’s Olympic 800m freestyle champion Rebecca Adlington.
However, as Murphy was over 20 seconds faster than the second fastest qualifier, she decided not to contest the guest final.
“We were more than happy with the time and the performances Gráinne put in this week and felt there would be no benefit in swimming the final,” said Murphy’s coach Ronald Claes.
“The plan was to come to London to get a feel for the venue and the surrounds.”
Murphy heads back to training at the University of Limerick and will then head to Denmark for further sessions ahead of the Danish national championships in April.
Nuala Murphy swam a heat time of 8:59.13 in the 800m freestyle.