The judge on Tuesday said that the prosecution had provided a compelling argument as to why Diane and her mother Adeline should remain on remand until their trial begins.
In the ruling, the judge, whose name was not provided, said that the crimes the two are accused of are sensitive.
Diane, 35, a vocal critic of President Paul Kagame, is charged with inciting public insurrection and forging documents, which she has consistently denied and labelled “politically motivated.”
Her mother is similarly charged with inciting public insurrection and separately with promoting sectarian practices.
“I know that you are powerless to deliver a fair verdict and to give me bail. You are trying my case but the real power and decisions will come from the President’s Office, not from you,” Ms Rwigara told the three-judge panel.
During the ruling Tuesday, only Diane was in court as her mother was said to have been ill.
Forgery charges attract five to seven years in jail, while inciting insurrection attracts 10 to 15 years in jail. Promoting sectarian practices attracts five to seven years in prison.