In many states a felon cannot be appointed. I do not practice in NE. If no one from NE answers this question, I suggest that you conttact an estate attorney in NE for the answer - look for an attorney in the county where the decedent lived becuase an attorney should represent you when you Petition to have her disqualified.
Certainly that issue should be brought to the Court's attention and then the Court can decide whehter a convicted felon can be appointed.
Legal disclaimer: This answer does not constitute legal advice. I am admitted to practice law in the State of Missouri only, and make no attempt to opine on matters of law that are not relevant to Missouri. This answer is based on general principles of law that may or may not relate to your specific situation, and is for promotional purposes only. You should never rely on this answer alone and nothing in these communications creates an attorney-client relationship. less