The problem is she could never play the 5 here. And if she can't play the 5 in college, she can't at the next level. She also never developed a consistent mid-range jump shot, so that pretty much eliminates her as a face the basket threat. So she can only play one position: the 4, and then only with her back to the basket. She has at the length and athleticism to be a good defender at that spot. What she does extraordinarily well is offensive rebound. She actually had 20 more offensive rebounds than defensive. I honestly can't remember another player who played as much as Saxton who could say that. Usually a low post player will have twice or more defensive rebounds than offensive rebounds. So she's definitely a role player. Some GMs might not want to spend a draft pick on a role player.
So to be clear, I respect her. I'm just giving you the reason why she's not projected to be drafted. The 3 point shot is a big deal in the WNBA, so Bibby's ability to be a threat for there is most likely the reason she's projected ahead of VS.