The 24-year-old Rivera finished ahead of Arlenis Sierra (Astana) and Cecilie Uttrup Ludwig (Cervélo-Bigla).
The peloton closed down the break as it readied itself for the expected sprint finish at the end of the 131.3km one-day race from Taino to Cittiglio.
"We had a couple of different cards to play today,” Rivera said. “We tried our luck in getting in any potential race deciding moves but it turned out that the race stayed together for a bunch sprint.
“We kept fighting to stay in the front group and it paid off. I was really thankful to have the support of my team and especially Ellen [van Dijk] there with me, she came back over to me at the last climb and stayed with me through to the end.
“She was instrumental in the finale and I couldn't have taken the victory without my team-mates."