Hello I believe I can help you with your concern
I am so sorry that your sister did this to you, and I can understand your feelings of betrayal with this.
I would like to ask a couple questions to get some more information, so that I can better help you
Has your sister ever taken credit for work in this manner before?
Has she ever taken advantage of others before?
And also does she expect praise for her work and does she think she is better than others at all?
I don't think she has taken credit for others work before, but she does seem to have a lot of tension with the people she works with. It's sort of a recurring thing. I chalk it up to how tenacious she is. She will hound you and hound you until you do what she wants. It drives me crazy.
When you say do what she wants, does that mean you have to do it her way only?
Oh yes!One other thing: She thrives off of praise and what others think, yet she still manages to tick people off regularly. She has this joke about about being the 1%. This comes from way before Occupy Wall Street--in fact, it comes from the Iowa tests from elementary school and how we always scored in the 99% percentile. She always is disappointed in how mediocre people are and holds up her own efforts in comparison and jokingly says, "1%."
She will not relent until you do what she wants the way she wants.
Okay, well it is possible that she may have traits from a personality disorder called Narcissistic Personality Disorder (NPD). She may not have the entire disorder, but it appears that some traits are present. Here is a link explaining it in more detail for you
Now I definitely do not think you acted irrationally at all and the fair thing would be to get credit for the work you did, but she may not have saw that or she may have had a lack of empathy to your concerns, all are possible when someone may have a diagnosis of NPD.
In addition, how to deal with your sister going forward will be difficult. I do not think you should help her with future yearbook or any of her projects unless she puts in writing your contribution (contract) beforehand. You have to treat this like a business arrangement, even though you both are family.
Also when you get mad or frustrated with her in the future, it is best to express that. Anger is a natural emotion and needs to be expressed in a healthy and assertive manner. This worksheet can help you with that moving forward with her.
Also these books are very insightful on NPD and can help you with your interactions with her in the future.
I really feel I was assertive with her once I felt she crossed the line, but the damage had been done. I can't sleep and I'm worried about seeing her when my whole family gathers this weekend as we'll be surrounded by kids and I don't want to say something in front of them, but am too upset to hold my tongue at this point.
I understand and that is a perfectly normal reaction that you are having because of what she did, but I think it would be best not to make a scene. But instead if you want to talk to her, you can call her over to a secluded part and have a discussion about it with her if you want to get something off your chest. Still it may not help you in this situation and I think that looking forward is the best strategy and planning ahead so that she does not do this again to you
I agree. My family is so important to me. And I certainly can muster up self control when needed. Thanks for your insight. I'll do some reading up on NPD and just watch myself around her a bit more.
I think that would be best, XXXXX XXXXX not want to this to happen to you again. I am happy that I was able to help you tonight. My goal is to provide you with excellent service, so if you ever have any further questions or concerns please do not hesitate to contact me at anytime.
You are most welcome :)