Fleeing the jurisdiction will always stop the SOL from running. So, hypothetically if the SOL were 4 years and she fled after 3, she could be prosecuted up to a year after her return. Since you don't say whether you are in state or federal court, or if the former, which state, I can't give you a precise SOL.
When you say she fled from prosecution you need to be more specific. If she just failed to appear in court but has not physically left the juristiction of the court, then there is potentially a statute of limitations issue.In the event a Motion to Dismiss is filed on behalf of the defendant for failure to prosecute with the statutorily required time period, the state attorney will have to show that the state has done a diligent search to locate the defendant and that the defendant was unable to be located within the jurisdiction. If the state failes to show that they have attempted to serve a warrant on the defendant after the failure to appear than there could be some issues as to the statute of limitations. furthermore, if the defendant can show that she has maintained residence within the jurisdiction the entire time, (i.e. driver's license address, phone bills, mortgage, rent, etc.) then there could also be some statute of limitation issues. I would advise that the defendant contact a lawyer within the jurisdicion of the court and explain the facts and circumstances surrounding the "fleeing" to determine what legal options are available.
More information is needed...for example, where the charges filed and then the person fled? If so, the statute of limitations will be tolled while the person is out of the court's jurisdiction.