Beyonce's halftime performance at the Super Bowl was significant for women. The majority of the time it is men who perform at halftime. The fact that Beyonce has become such a huge name and icon says a lot. Her not only performing, but performing well was really big for all women.
How would a Super Bowl halftime show be significant for women in the first place? How would it be anything aside from showcasing acts who have already become famous and successful prior? Many women (Madonna, Britney Spears, Shania Twain, etc.) have performed before, and Beyonce has been to the Super Bowl before already.
Beyonce came out dressed to show her sex appeal as much as she could without getting into trouble and she sang songs of hers, none of which were less than five years old. Guess what, that's been done a few times I don't see how it in this instance could have been significant for women, or for anybody else for that matter.
Her performance is not significant for women because women have been headlining Super Bowl halftime shows since the 1970's with Carol Channing and Diana Ross in the 1990's. She was far from the first female performer headlining such an event. As a matter of fact, her performance might have been demeaning to the progress of women considering how Beyonce's main focus throughout her performance was to show off her skin.