Part of the 'overlooking' is also because her career stats are limited by her being limited to 3 years. If you add another year of stats at the end of her career she would be second or third in steals.
Also, her assist ratio and total assists numbers aren't great - for her career she had a 1.09 A/TO, and as a junior and senior she totaled only 113 and 149 assists, and her senior year was her best with a 1.57 A/TO - as a comparison Hartley had a career 1.52 A/TO and as a junior and senior it was 1.58 and 2.08.
Career A/TO for the others:
Bird: 2.11
Jefferson: 2.64
Montgomery: 1.8
Rizzotti: 1.56
DT: 1.84
Dangerfield: 2.59
Bird played 118 games and had 585 assists, Williams played 109 games and had 286. Hartley with 559 assists in 153 games, and Dangerfield with 599 in 134 games are the only ones listed above with fewer than 600 assists. For her career Williams average 2.6 assists per game, Hartley averaged 3.7 and the others averaged more.
I am not disparaging Williams, but Uconn has had seven exceptional PGs all but Dangerfield also won NCs - it is easy to get overlooked when surrounded by such greatness. She had tough luck when teammates went down with injuries as well (Sales and Ralph might have made a difference in how her last two years ended.)