My daughter has asthma/allergies and takes Flonase, Flovent, and ...

My daughter has asthma/allergies and takes Flonase, Flovent, and Albuterol as needed. Recently she started on Singulair, and she's been behaving horribly, saying mean things, yelling at us. And now she's started saying things like she wants to hurt herself, that she's stupid, that she doesn't like herself. Tonight I was giving her her dose of Singulair and my husband asked if maybe the medicine was causing her symptoms. I immediately wished I had not given her that dose, but it was too late. I came right to the computer and found this site. I'm so distressed reading about other people who are irritable and can't sleep, she hasn't been able to fall asleep easily the past several days, now I think I'm understanding why! I'm immediately stopping this medication. I just wish I knew how long it would take to get out of her system.