Wills are rarely filed with a surrogate's court but that is the first place to look. You should consult with an attorney to determine what happens...

You should consult with an attorney in the state where you believe the decedent was domiciled at the time of his/her death. As noted by attorney...

What can I do to get her to pay me, without hopefully needing to hire a lawyer ?

Go back to the attorney who handled your divorce and get help. I don't think you are going to be able to engage in motion practice on your own.

Do siblings have to be bought out in this situation?

There are not enough facts to advise - for instance has an estate fiduciary been appointed? - is there a will.? You will need to see a probate...