Originally Posted by Steve M

Nope - this isn't going to work. It's true to say that in order that if she is leaving the US by land and not planning to return during the current stay and depart before the expiration of the current I-94 form, then she must hand it in at the land border before departure to avoid being considered an "overstayer" and having problems the next time she visits.

US Immigration law specifically deals with visits to neighboring countries (Canada/Mexico/Caribbean) and says that visits to those areas do NOT reset the clock, so to speak. Stays in the US immediately before and after to visits to those areas are considered a single continuous stay in the US. Whether or not you hand in the I-94 form upon the first departure is irrelevant.