My cousin who is a 14 yr old can't control urination while laughing. she urinates the whole of it. why does this happen and what to do about it?

Giggle incontinence: Great to help out your cousin. She has well recognized form of incontinence. 1)best for her to empty her bladder as often as it is convenient, especially before situations where she knows she might laugh. 2)try kegel exercises. 3)consult pediatric urologist who will have experience in managing this problem with medication. Ritalin (methylphenidate) or Concerta are classic meds for this problem or anticholinergics.