She shouldn't be violating copyright rules if she is 1) giving credit to the photographer and not passing off as her own work 2) isn't making money off these pictures or causing the photographer loss of wages from the pictures.
It could be argued that she is doing this (the bit I bolded). Because the OP posted them on FB, Great Aunt Sally no longer needs to buy the photos - she can view/download/print them for free.
I have no idea of the actual law around it, but I could see the photographer arguing this point.