What do I do if a classmate is acting weird?

I am currently in a state of question. I am in a class of 30 people. I am usually the quiet kid, speaking when I feel like it’s best and mostly listening. I spend most of my day in my desk or speaking to others, though it is not as often. However, a girl in my class approached me about 2 weeks ago. I, of course, thought it was a lone incident and that she was pranking me or something, as I have not talked to her that much over the year. However, one day she started texting me. I was unsure why, but she just started with a simple “Hi.”. At times, she would ask me random things or just message out of the blue. A week ago, while I was doing a practice test at school, she approached me and asked what I was doing. Of course, I told her and she asked me if it’d be okay for her to help me with the test. This is the part that got me into thinking if there was something else involved in this thing or if she did it because she was bored, but she stayed there till the end of that hour. The other conversations are normal, but I uncertain, since I was never approached like this before and I get mixed messages here. And if there really is something, what should I do?