A police report which found no proof of the charges against Hossain was accepted by Dhaka's Fifth Women and Child Repression Prevention Tribunal, which also scrapped a "non-acceptance" plea by Happy. Both were present in court.
Her lawyer, Tuhin Hawlader, said they would appeal against the order in the High Court.
Happy said she and Hossain were in a relationship for nine months last year, but he refused to marry her. She filed a lawsuit against him in December, accusing him of luring her into an affair with false promises of marriage.