ok found it it was hiding...ive done a map to show the coverage of the part of the tower she was logged onto (looked on google earth 2008 to see which direction each transceiver pointed)..if u don't know a cell tower has 3 "transceivers" spaced 120 degree apart in a circle..the cell phone logs in via the one covering that area.......it also shows that if the couple arguing on the bridge by the uni drove off to the right then the phone would have logged onto the next transceiver round..of course it could go to the left and stay logged in on the one it was on....
make of it what u will..i think her phone didn't go far from her house
ill see if I can find out what network the tower belongs to and where there next tower is