My Daughter Is 13 She Has Had About 11 Cycles

my daughter is 13 she has had about 11 cycles always started about the same time, this month shes 7 days late. she is in a wheelchair and has cerebral palsy she is never without us so pregnancy wouldn't be the reason. Ive read the various reason she could be late, the only thing would maybe be if she is having emotions stress. im just worried how long do I wait to contact her dr.