that's not going to tell you the wear and tear on the belt...that's just the tension which may be a bit off.

to check tension:
-remove valve cover
-remove upper timing belt cover
-mark timing belt across camgears/belt
-make 3 full rotations of the crank
-see if the marks line up again (or if they are off by the same amount)
-if they are ... it's tensioned properly
-if they aren't ... you belt is jumping teeth and your lucky you haven't fucked up anything just yet


to check wear and tear:
-look at belt
-see if any threads are showing
-if so
- how bad?
-if not
- check for part number (on belt)
- check for date written (on belt)

that should give you a better idea besides her word for yours