Hello my friends out there-

My sister in law has a habit of inviting our family to special events only to give the cold shoulder to each and everyone of us when we attend. Time and time again she does this in front of her family but when she is alone with my mom or I shes a normal human being. Its not like she doesnt see her family she sees them regularly but at these family events she doesnt bother to say hello or even send a smile our way. I' ve tested this behaviour time and time again. She behaves like we are not present at the event. I dont understand this behaviour, what message is she trying to convey to the family when she does this? I would never treat any of my invitees like this please pour your wisdom on me. I'm seriously thinking of never attending another event because she makes me feel so uncomfortable.