YTA. They really both needed their own birthdays, and it was your responsibility to make sure those birthdays were proportionate to one another and fair. Nora may deserve them, but Amy doesn’t deserve to have her gifts taken away. (Edited)

If your family is so nasty as to send gifts to one child and not the other, then I’d recommend making up the difference for Nora’s party(ie. If the family buys Amy extra gifts, try to source extra gifts for Nora that are similar, or that are things she really wants), and excluding them from family festivities until you can sort out if they really don’t consider the other girls part of the family.

If it’s a financial overload, then find some agreement where you can hold the girls birthdays further apart, or start getting their gifts earlier in advance, by a few months.