Hello - My 13 Year Old Daughter Took 1/2 Tablet

Hello - my 13 year old daughter took 1/2 tablet of over the counter melatonin last night at a friend's house to help her fall asleep. She was supposed to start taking Zoloft tonight for social anxiety disorder/panic attacks. Is it okay to start the zoloft tonight? Or should she wait a couple of days to rid her system of the melatonin she took last night? Other than the melatonin, which was a one off, she is not on any other medications.