i don't think that elsa have those power since birth. she probably................ Spoiler ate a devil fruit of winter. when she was little she was playing in the fields when she finds a mysterious fruit; she ate it and now was curse with power.
maybe it was mixed into her baby food and they jsut assumed she was born with them when she exhibited powers at an early age
that's what i'm saying or the mother had eaten the devil fruit and elsa consumes the power I know what it means but i might as well make it into a joke because no one believes that I'm the most funniest member