Guica, from La Prairie, Que., started the day with a quarter-final win over Cuba's Gretter Romero, then downed Angelica Delgado of the United States in the semifinal before losing to Brazil's Erika Miranda in the final.
"The fighting here was really great, but is sucks to end on a loss," Guica said. "I lost to her twice before so I was trying to do something different and she caught me again."
Canada missed out on a second judo medal when Sergio Pessoa of Montreal lost to Yandry Torres of Cuba in the men's 60-kg bronze-medal match.
In the women's 48-kg event, Calgary's Erin Morgan lost her quarter-final match to Isnadrina Sanchez of the Dominican Republic.