3 year old need mommy advise

So my 3 year old daughter , has been really acting out the past couple of months, and I mean BAD. She won't listen to me and my fiance , won't potty train, screams, nothing affects her, " really talented in fake crying" its just non stop trantums,but when she's with my mom she fine and she listens. Now we know what the problem started from my grandparents. my papa is really bad about letting her get away with stuff like paci, potty training letting her run from them.

For example it was my birthday june 12th so we all went to dinner at chedders.Well my daughter "Cassidy" decided to start acting up like standing up and and looking over the booth and disturbing people. so I tried to correct her and my papa immediately says he'll take care of Cassidy.well go back to eating, and talking, all of,a sudden my papa starts letting Cassidy walk around the restaurant. disturbing disturbing people and me and my mom try to get her to come back , and my papa goes full blown out on us yelling he got it. worst birthday ever .

Felt really embarrassed and other people in restaurant just shaking their heads and asking for manager. I Really don't know what to do , i don't know if I should keep Cassidy from my grandparents for a while and see if that helps her or what.I really need some mommy advise.