Is the number of total molecules on the left side of a balanced equation always equal to the number of total molecules on the right side of the equation?

No, the total number of molecules can be equal or not between reactants and products  when a chemical equation is balanced.

Her conclusion that 90% of the student body wants the colors changed is an INCORRECT conclusion. The 90% out of 100% is not referring to the total numbers of the student body.For example, 100 people are members of student body if only 50 members responded the survey, then we have:
 90% of 50 members who answered the survey said that they want the changed.