I think that is true. To an extent. When you’ve put yourself out for another person time and time again (as @TatinG referenced) but that it seems your effort is not appreciated, when do you stop putting yourself in that position?
It sounds to me that TatinG was disappointed and expressed her disappointment. But in expressing her feelings, her sister and niece are discounting the fact that by excluding certain family members, there is bound to be hurt feelings. It’s not just being excluded, it’s also being the person blamed for the fallout.