Number whatever your are trying to find out is broad and i dare to say there is no rationality in such attempt for simple person .It is irrelvant at this point of time and always ,unless you are doing a research on human psychology.A human behaviour would be the answer.Is her cheating jutifiable ..NO..but do people do that ..YES...Not only girls guys also do this sort of stuff. Move on ! my fren that is the best solution we are in materalistic world.