Reevaluated symptoms and conditions

My daughter had been on singulair from the time she was 8 yrs old until she was 14. This will sound as if I am a horrible mother but I just thought that she was a raging bitch. Without my knowledge, she stopped taking her Singulair for a few months and she became a different person. She was so sweet and loving. One night she came in my room having an asthma attack and I asked her if she was taking her meds, she admitted that she had stopped taking her singulair and I got on to her and immediately got her prescription refilled. Within a few days of taking the singulair she turned into a raging, screaming emotional wreck, a TOTALLY different person. I feel so bad that for 6 years of her life I put her on medicine that caused her to have screaming, uncontrollable tantrums, and severe mood swings that caused her to be miserable. It does seem to be the only thing that effectively controls her asthma symptoms but the emotional havoc that is causes her and the people around her is not worth the benefits. We have an appt. with her doctor to see what other options we have.