The law isn’t exactly clear on that issue. For now, the answer is no. Her retrial at the appellate court level can be handled in absentia, so she will not have to attend. If she is convicted at the retrial, it could get complicated. Italy would likely seek extradition, and would request the U.S. government to turn her over. She would then contest the extradition, on the grounds that her retrial would violate her Constitutional protection against double jeopardy. Italy would argue that the trial had not been completed, and that the appellate process was just an ongoing segment of the same trial. That would not fly for an American trial, but apparently there is precedent with some other countries permitting extradition in similar circumstances. It will also depend on the specific langauge of the treaty that the U.S. signed with Italy. At this early stage, it is unclear whether she could end up being extradited if the conviction is reinstituted.