Hi, your mom is going to continue exploring whatever good will is left among your family members until she has burned all bridges and her relationship with everyone is shot. One way you can save her and everyone else from this fate is doing what should have been done ages ago and it’s this: say ‘no.’ When everyone tells her no, she can’t stay with them for half the year and needs to find a second home to live in when she wants to be in town, she will really have no choice but to finally change her behavior. But as long as someone – anyone – is saying yes, no matter how begrudgingly and no matter how much of an inconvenience she is, she will keep crashing where she has outstayed her welcome.
You write: “There’s just no nice way to say that we’ve all had it but, we’ve all had it.” The problem is that you’ve been too focused on being nice. And where has that got you? It hurt relationships with a large number of your family members – probably the thing you were hoping to avoid by being “nice.” Stop being nice, and be kind instead. Kindness is when you think of people’s best interest, and it’s in everyone’s best interest that your mother (and sister) get a home of their own. And they’ve proven that that is a last resort after everyone else tells them “no.”