I am sorry that you and your family are facing this. You should talk to her attorney. With your sister's permission, the lawyer can tell you what the possible range of sentence is (the plea agreement that your sister signed will be fairly specific). Then the attorney can inform you of the adjustments and departures that may apply to her sentence. The federal sentencing statutes were written to apply so that everyone in the same circumstances would receive pretty much the same sentences, to eliminate unfair sentencing disparities. Judges once believed that they were obliged to apply the sentencing guidelines as if they were mandatory; a U.S. Supreme Court case finally announced that the guidelines are not mandatory, but are simply "advisory," but judges tend not to depart from the guideline system too much. Still, it depends on the judge, the prosecutor, the probation officer's report (not that she will get probation -- that is probably a legal impossibility -- but the probation officer writes a report with a calculation of the sentence that should be imposed according to the guidelines), and the defense attorney. You may even have information that would help her defense lawyer form arguments for departures and variances, if she has somehow failed to mention certain life circumstances to her lawyer. I am attaching a link to a Wikipedia article about the federal sentencing guidelines. It is a very basic explanation and may not be completely up to date, but it will give you an idea of what she and her defense attorney are dealing with in preparing for sentencing. Some defense attorneys find it useful to provide the judge with letters from family members, or to present testimony from family members on behalf of the client. Try to contact the lawyer who is fighting for your sister to see if you can help. Also -- her kids may need counseling to deal with this disruption in their lives. And you may need legal documents to assure that you have the authority to deal with schools and medical providers for them in their mother's absence, and to deal with their father in the way that you and your sister anticipate. Child Protective Services could seek to permanently remove them from her life if these things are not taken care of. You should talk to a lawyer about those issues, and a public defender is not authorized to resolve those matters -- they are assigned only to defend her in the criminal matter. My heart goes out to you. Good luck.
A true attorney/client relationship has not been established by your question(s) and my response(s). Your question(s) and my response(s) are limited and general in nature. You cannot rely on the information in my reponse(s) because correct legal advice in any situation requires that the client provide many more facts. The addition of one seemingly small or minor fact could completely change the response(s). When you put information about a legal situation into a public forum like this one, anybody can read it, including the police and prosecutors, and anything you say can be used against you in court. I recommend that you establish a true attorney/client relationship with a lawyer who can then find out, through private communications, the other pertinent information needed to provide an accurate, safe, reliable answer for you.
I agree with much of Ms. Lutgring's answer. I write separately to note that post-Booker, (the Supreme Court case that made the sentencing guidelines advisory only) federal sentencing law takes into account the sentencing guidelines as well as the individual circumstances of each defendant's case. So the average sentence imposed on other defendants is not all that relevant to your sister's situation. Talk to your sister and her attorney to get the best information on her individual circumstances. As an aunt who has stepped up to raise your sister's children, I commend you!
Asking, "How much federal time," is not an easy question.
This is yet another example that what appears to be a relatively simple question is not simple to answer unless ALL the facts and an actual (not a paraphrasing) review of the court record is conducted by an experienced federal criminal defense attorney.
Of course, every answer is based on the question asked and requires a more complete context. This answer should not be relied upon to make a legal decision. Seek the advice of an experienced criminal defense attorney before acting. Law Offices of Raymond G. Wigell, Ltd. Defenders of the Constitution since 1975/ Aggressive Creative Defense Strategies/ Website: www.waaltd.com 24/7 --(708) 481-4800.