Ever since I began University this year (just completed my first year), I've been having recurrent issues with girls. I'm not a social person at all, and I don't go to University to party/drink/socialize as most people seem to do. I have a few friends, but most of them are just friendlier-than-average acquaintances as I find devoting oneself to making friends uninteresting and a waste of time. However, the largest girl issue to date, not to mention one that pervades in my memory, began like this:
A few months ago, as I exited a gym near our campus, a girl approached me and asked me for a ride to her supposed residence. This girl happened to also be in a few of my classes. Wanting to avoid an atmosphere of awkwardness between us whenever we had to interact in our classes in the future, I said sure. As we were driving to her residence, she tried to create a relaxed conversation a few times. I'm not that sociable at all as I'm fairly introverted, so whatever topic of conversation that she attempted to bring up would not spiral into the jaws of randomness, but rather they would end from a concise answer from myself. As we reached her destination, she asked me for her number saying that she appreciated the ride. I said no problem, and then carried on with my usual business as I drove home.
A week later, she asked me for some calculus help (one of the classes we happened to share), and I ended up aptly helping her with what she wanted. A few days later, she began text messaging me rapidly (once every few minutes on average) about miscellaneous subjects. I occasionally responded out of sheer politeness, but I suppose she took this as enabling towards her excessive sociability. Eventually, she asked me out, and I said "no, thanks" at which point she finally stopped messaging me.
Following this, I got told to my face while on campus by one of her friends that I was an asshole as well as that I apparently thought that I was "too good" for the girl in the aforementioned incident.
This is just a single example of what has happened throughout the year. Frequent drama involving seemingly overly social girls who apparently are not used to handling rejection of any kind. It's not that I dislike the girls making the advances per se, but I'd rather be left alone as I don't enjoy unnecessary social interaction. I'm not sure what to do as I don't like being too assertive as well as the fact that I tend to be really polite.
What can I do to stop this? I just want to be left alone so I can quietly study without causing or being involved in any social drama and so on.