Can My Sister Who Takes Olanzapine Take An Otc Kirk

Can my sister who takes olanzapine take an otc kirk land sleep aid doxylamine succinate with olanzapine to help her sleep. The doctor told her to take melatonin 3mg. I take kirland and it works so much better than melatonin for me. My ? is will it interact if taken togeter (melatonin and kirkland.
Robert