A scientist observed the boundrary between teo tectonic plates for a decade and finds that no new volcanoes have formed over the course of her investigation. Does this result suppor the theory of plate tectonic? Why or why not?

In fact a 10 year period is not very much in geological time as plates move at something like a few centimeters per year so it can take millions of years for features like volcanoes to form. It is as James Hutton said that it takes tremendous amounts of time for geological events to take place and it is not to be expected that much will happen in decade.