Haughey, 27, returned to competitive swimming in April after taking a four-month break to consider her future.
She clocked a time of 1:57.38 to finish runner-up in the 200m freestyle on Thursday, adding to her 100m freestyle silver the day before at the Spanish city.
Barbora Seemanova of the Czech Republic topped the 200m freestyle podium, with a time of 1:55.85.
Portugal’s Francisca Soares Martins rounded out the top three, touching home just over two seconds behind Haughey at 1:59.54.
Haughey fell just short of a third medal in Barcelona, as she came back fourth in the 50m freestyle at 25.19 seconds.
Nevertheless it marked a stellar few days for the four-time Olympic medalist – she landed two medals in the first leg of the tour in Monaco after winning both the 100m and 200m freestyle.
Fellow SAR swimmer Ian Ho, meanwhile, withdrew from the men’s 100m freestyle event in Barcelona.
The third and final stop of the tour begins this Saturday in the French town of Canet-en-Roussillon.
