My moms and sons relationship

My son is 18 month old and my mom watches him 2x a week while im at work. Everytime shes over hes always whining and crying around her asking to be picked up and just wants to watch tv (she always has the tv on for him). The moment shes gone hes normal again (calm). Is This because she gives in his negative behaviour? He wants nothing to do with me when im home with my mom.