Legal Question in Wills and Trusts in Illinois

I do not find this to be an unusual decision by your mother. If this has been your sister's home, your mother may have felt it was appropriate that she be able to continue living there. That would especially seem likely if she was a significant help to your mother, for example if she was a caretaker.

Absent provisions addressing the future expenses, I do not see that those should come out of the estate. Your sister will need to be able to take care of the property and pay its expenses. If it looks like she is letting the property decline, you should see an attorney.

Absent evidence that your mother was impaired in her thinking or under some undue influence, she is presumed to know her wishes and what she wished was for your sister to use the house as her residence indefinitely. Your mom had her own reasons, and her honor is not impaired by providing for your sister. Is it possible that your sister has greater needs than you or your brother? Even if you and your brother can't understand your mother's thought process, I urge you to move on with your lives and your own families. Unresolved resentment against your sister or your mother will not serve any meaningful purpose nor provide any benefit.