Am I overreacting - my biological family continues to get together on a day they know I can not attend

I was adopted at one month old and found my biological family after I graduated from college decades ago. When I found my biological mother I just wanted to get family and medical history and was open to more if she wanted that too. What I discovered was I had three full younger siblings that did not know about me and I did not know about them. We were all shocked and my sisters were not too happy with our mom about this and other reasons she is not really the motherly type. I found out my bio parents were Mormon and young and conceived before wedlock and hid the pregnancy. They got married while pregnant with me and gave me away at birth but apparently I was in foster care for a month in case they changed their mind. My bio parents went on to have three more daughters after me who they kept. My parents who adopted me lived 15 miles away and did not know any details about my bio parents except a piece of paper with vague details as it was a county adoption, I had a strong feeling to look for my bio family for years and I think it was to find my sisters. My bio parents went through a nasty divorce when my sisters were young - it was a toxic marriage and my bio father was physically and mentally abusive to all of them.

For the last 30 years my new found sisters and bio mom and myself have been like a family. My adoptive parents when alive were hurt at first that I found my bio family but soon changed their feelings when they met my sisters especially the one with the same first name as myself coincidentally- they loved her. We all spend holidays together, raised our kids seeing each other etc. and been a big part of each others life except one sister who is aloof and has strained relationships with others and keeps a polite distance from me which is fine.

Nothing is perfect but they have been a constant in my life for a long time and I love them and I know they love me. I thought until recently. We get together about 4 times a year together and see each other one on one other times. The last time they all got together one person suggested on group chat the one day I always work because she works on the other days. I said you all have fun and then I faced timed them from work for a few minutes. A few months later - today - there was a group text but I did not see it until much later where they were talking about getting together. By the time I saw it they all decided to get together again on the only day I cannot - they all now I work on that day. Not one of them said let’s wait to hear from me or mentioned that day would not work for me.

I have done a lot of counseling over the years but this whole situation really triggered me. I am very hurt and obviously as the only one not raised in the family feel very left out. I had a good life with my parents who raised me and glad I missed the toxic life unfortunately my sisters faced. My sisters are openly happy I had another chance in a more stable environment somewhat - my situation was not perfect either, I respect the fact they may want to do things without me but that has never been the case. But now after all these years I never thought there was a problem until now, I just want to exit the group chat and part of me wants to block every one of them as not one person waited to hear from me. I am too old to have people in my life who don’t feel the same about me. I know my reaction is intense and I think it is because this apparently is a very deep womb that I thought was healed but this just ripped my heart open and I cried. I want to protect myself and telling them I am hurt doesn’t make sense since they all know I could not attend. Am I overreacting?