14 year old virgin with a lot of milk in her breasts

My daughter is a 14 year old mentally disabled child who will be 15 next week. She was prescribed Risperdal last month. Her doctor wanted her taking the lowest dosage ( 0.5 ). She's non-verbal. So to get you to understand her wants and needs she uses gestures. I noticed since she has been on the medication that she is always wanting to be held. Was very quiet. Sleeping a lot. She wasn't constipated like the others here have brought up, but she always had diarrhea. Was gaining a lot of weight as well. But it was what happened this morning that made me panic. When I was giving her a bath this morning I noticed that she had a white drip on her leg. I didn't think anything of it because it looked like the liquid bath soap. She gave me a hard time to take her out of the tub, so I put my arms around her from behind causing me to put pressure on both of her breasts. Milk shot out from both breasts. Noticing the discomfort she was having I squeezed out as much I could from both sides. There was literally enough to feed breakfast to a baby. Of course as the mother who knows for a fact that her daughter is a virgin I began to panic. With the recent weight gain and the enlarging of her breasts, and now this, my mind began to think negatively. It has only been 3 weeks! Is this drug that bad that it could cause such a thing in such little time?