Look at what she has going on in her life. If she's someone who's focused on her studies, and on her spare time is perfecting her skills at playing piano, and also does dance classes on the side, and then spends lots of time with family and friends, and is involved in church community stuff, safe to say, she probably doesn't have much time to be seeing anyone..
Some people are fulfilled in life through so much more, that they don't actively pursue any type of sexual relationship or otherwise. These people are generally the most happy and content in life.. and often times, they find relationships and good partners naturally because they don't actively pursue it and just live their lives and focus on what's in front of them.
So don't think that any single hot girl or all single hot girls are going to be messing around.. Yeah, sure its safe to say many will because the way our society is programmed and if you even took a look at some of the content that's pushed towards women, whether a woman's blog, Cosmopolitan, by women influencers on social media, quite a lot of it is about sex and dating..
Like I mentioned, look at their activities, hobbies, what kind of content they post online, and you can assess it from that.
But at the end of the day, you shouldn't be too concerned with any of it.. Because there's also chances that they do have all this stuff going on, and their focused on much more priorities, an can still be sleeping with someone or multiple guys. Only way to really find out is by asking them, if you're in a position to do so comfortably.