So, my father, my bf and I have been at my parents house canning some veg for three days now. I decided I would make dinner for everyone tonight. My sister and her family show up out of nowhere and are hanging out. After a while it becomes apparent that they've decided they're "inviting themselves to our dinner". I catch on to it and decide I'm going to wait them out (because I think it's rude as hell to invite yourself to ANYTHING that you weren't invited to) and we've all recently eaten anyways at 6 so none of us are actually hungry. She starts to get bitchy because her kids are complaining that they're hungry because they haven't eaten since lunch, they're 6 and 3. She keeps yelling at them to wait until dinner and keeps making comments about when dinner is going to be made. So my bf decides to start making dinner (while we're all still in the middle of canning) without telling me subsequently giving in to my sister's demands. I get pissed off and decide to leave. (Btw, she does this ALL the time. She tries to invite herself to anywhere she thinks she'll get a free meal or whatever and I'm sick of it). Am I just being rude or am I justified in being pissed and walking out?