During the 1920's and 1930's vandalism was a major issues during Halloween parties. Schools and towns had many issues controlling the problem no matter how hard they tried. Fortunately, by the time the 1950's rolled around, Halloween was mostly celebrated in homes and classrooms instead of giant parties. The target audience was also children, who were much easier to control.
If the italicized sentence is <em>how eager she was to do her best, </em>then the answer would be an adverb clause. Because the whole clause acts as an adverb.
