I am wanting to know if I have a right to be mad at my sister in law?

Here is a little background. My husband and I have been married nearly three years. He has adopted my child a six year old. His mother is dying of cancer right now she is on hospice at home and is not doing good at all. She is remarried and her husband has grandchildren as well. The sister in law takes over only one of my father in laws grandchildren and does not show any of the other children the same kindness. She acts gets this child every other weekend and when she has her acts like this is her child. Also on FB her and her friends put update all the time about my mother in law but do not include my husband for example one of her close friends put please pray for Becky(my MIL who is sick) and continue to pray for the "girls" and Gary (my father in law) Another thing they ordered shirts to raise money for my mother in laws expenses and we did not order our shirts the first day they put them on sale but took her the money the next day well our shirts did not get ordered. She said they will be ordered the next time which will be the next week. So my husband goes to work today and his mother worked at the same place when she was able well everyone has on their shirts today. Then he went to the bank where my sister in law works at and they all have on the shirts as well at the bank. Then he goes to the other bank in town where we have a loan and he needed to pay they all have the shirts as well. I understand about waiting on mine and my childs and my mothers and grandmothers shirts can wait but you are not telling me she could have not swapped out my husbands order for someone elses, and got them on the next round? Am I just overreacting? Also my husband went to visit his mom a couple of days ago and she was able to open her eyes and speak to him just a hello but she had not spoke in five days well later that afternoon the sister in law puts on FB "I guess I am just going to move in with mom, she had another good morning and talked to Wesley (my husband) and Gary(FIL) I miss eveything" This is just really making me mad and I dont want to say anything to her because their mom is dying but I am tired of her treating my family like we are nothing to them. What do I need to do?