They have competed together for several years, coming fifth at the Olympics and taking European gold in 2012.
However, Couch was paired with 16-year-old Lois Toulson at last week's National Cup, where they came second.
"It wasn't great, to be honest," Couch, 26, told BBC Spotlight.
"Especially as we're leading up to the World Cup in less than a month, so being apart for a month and a half was not great preparation for it."
The duo are hoping to secure an Olympic Games qualification spot at the event, which is also being held in Brazil.
Barrow had been dropped from the 10m synchro line-up following a series of shin injuries but the Plymouth divers have been selected as part of a 15-strong GB World Cup squad, which includes Tom Daley.
"We're just going to put it to the side - we're back together in synchro now so there's a lot of hard training coming up," added Couch.
Great Britain diver Tonia Couch has admitted her split with 10m synchro partner Sarah Barrow was "not great preparation" for next month's World Cup event in Rio.