Ho was found guilty of participating in an unauthorised assembly.
During the trial, Chow, a former leader of the now disbanded Hong Kong Alliance in Support of Patriotic Democratic Movements in China, had argued the annual vigil was "their right, their freedom".
Ho earlier told the court that "remembrance is resistance", adding that she only went to the site to test the difference between Hong Kong and mainland China, where any commemoration of June 4 is taboo and can lead to imprisonment.
Sixteen other activists are already serving sentences of between four and 10 months for the same incident.
After mass pro-democracy protests in 2019, China imposed a sweeping national security law that punishes offences such as subversion and secession with jail terms of up to life.