From Dr. Burrascano's Lyme Disease Treatment Guidelines:
TICK BITES - Embedded Deer Tick With No Signs or Symptoms of Lyme (see appendix):
Decide to treat based on the type of tick, whether it came from an endemic area, how it was removed,
and length of attachment (anecdotally, as little as four hours of attachment can transmit pathogens). The risk of transmission is greater if the tick is engorged, or of it was removed improperly allowing the tick's contents to spill into the bite wound. High-risk bites are treated as follows (remember the possibility of co-infection!):
1) Adults: Oral therapy for 28 days.
www.lymenet.org/BurrGuide200810.pdfI wouldn't try to figure out the risk - I would just do it. 28 days is nothing compared to what will happen if she gets lyme.