How can we force someone to open probate?

Sister had father sign a new will 4 days before he died. It leaves everything to her grandson who she has raised, he is 15. This was done in an attempt for her to keep getting welfare and she told people she is trying to just hide that he died for three years till the grandson is old enough to put it in his name. She finally filed the will in a far away county but did not open probate and has no intentions of doing so. The other sister was going to go open probate and force her into it but decided not to and we can't afford a lawyer. She did not tell any of the siblings he had died and hasn't to this day months later. A friend came and told them. She wants to hide it because she get a 315,000 paid for house and she is on welfare and driving a brand new car. Can we other siblings be held liable in any way? She is not opening probate so debtors cant find out he died. She gets everything so what can we do to make sure no debtors come after us later after she has sold most of his belongings except the house.