Has my mother in-law over stepped her bounds?

Me and my fiance have 6 children between the two of us (3 each) that we have full custody of. Ages 13yr, 12yr, 8yr, 6yr, 4yr, and 2yr. My 3 step children's birth mother hasn't been a part of their lives for a long time, and wasn't much of a mom when she was around. I have gladly welcomed them as if I had given birth to them. They call me mom, tell everyone I am their mom, and seem to be truly happy and feel safe now. The only one that seems to be having trouble with this is my mother in-law. At first she seemed thrill but as time goes on she does things that make me question her true feelings. I get along very well with all my other in-laws. Just the other day my mother in-law informs me and my fiance if when my 8yr old step daughters 9th birthday party is and what is going to happen. She didn't ask us for ideas or what date would work or any kind of detail for the party. She just planned the whole thing without ever consulting me or my fiance. Due to this my 3 children won't be able to be there because they have to go see their birth father in another state that weekend and I'm stuck at work. We were planning on having our daughters birthday party the weekend before so that everyone could be there but my mother in-law never asked and just made all the reservations without us. This comes after she ruined my 6yr old daughter birthday a few months ago by getting physically violent with my fiance at my uncles house(she shoved him and was yelling over one of the kids being put in time-out), and ignoring my two older step son's birthdays. I feel that she's greatly over stepped her bounds. Am I just being to touchy about it or not?And how do i handle this without it causing to much of a fight?