Many girls who reach this level are not the sexually and emotionally confident vixens that chase has described in this article. Oftentimes when we rack up so many sexual partners, we're lacking in some confidence or self respect. It can also be a newfound freedom thing (like being fresh of to uni) or trying to prove something. I know I picked up a good many when I got out of an abusive relationship, because all I'd heard for 4 years was "Who else would ever want that—want you? You're so lucky to have me." Turns out there were 13 gentlemen who were quite happy to have me. It made me feel a good deal better.
There could be any number of reasons she had that many partners. If it still makes you that uncomfortable, talk about the WHY. Otherwise? If you can accept that, it sounds to me like she's done counting for a while (;