As long as the cause of the grudge isn't enforced and instead you both work together then it should be passable but will need working on.
You and your mom need to both be on the same page so you work together and your little feather bundle knows a consistent identical response from both of you. Unfortunately what you mom did really didn't go down well and little one is perhaps now afraid of this reaction and probably didn't understand the reaction and its association with the "crime" hence deciding to totally avoid your mom for doing it in the first place.
Roz is way better at the training and explaining than me by 100% she's done the parrot training courses! Better we tag her and see what she thinks and how to get around it all @Roz
You and your mom need to both be on the same page so you work together and your little feather bundle knows a consistent identical response from both of you. Unfortunately what you mom did really didn't go down well and little one is perhaps now afraid of this reaction and probably didn't understand the reaction and its association with the "crime" hence deciding to totally avoid your mom for doing it in the first place.
Roz is way better at the training and explaining than me by 100% she's done the parrot training courses! Better we tag her and see what she thinks and how to get around it all @Roz