I know how you feel. My daughter gained 40 pounds in less than 3 months while on Risperadol. She took Cogentin for the tics, it works for some side effects but not weight gain. It is hard especially for girls. My daughter also took Seroquel for a short time and did not like that medication either. She didn't stay on it long enough to gain weight. She refuses to take any medications that have weight gain as a possible side effect because of the Risperadol. She was very uncomfortable being that heavy. I understand that you are concerned about depression. My daughter told me that she would end up depressed if she had to stay on the Risperadol because she didn't want to be fat.
You can't win. It's like you are stuck between a rock and a hard place. Has she tried anything in the same family without weight gain as a side effect? I know my daughter went from the Risperadol to Geodon and did much better. No weight gain at all. She actually like taking the Geodon.
Hang in there. 