Was the tire slashed on the sidewall or in the tread? Running over a piece of glass or metal can slash a tire through the tread. More like paranoia on her part. However, I think she should take the threat seriously and drop from public view for a while. A long while.
My last two flats were due to sharp pices of scrap metal stuck in exapansion joints of overpasses. Sliced through the sidewall both times.