Its her way of telling you not to get any ideas. In other
words, keep your distance. She do not want to be linked to
you.
Yes, you know each other for two years, yes she can be a
good girl. But what makes you think she really loves you? She
knows you fancy her. Therefore before people start whispering that
she is your gf, she treat you like shit. So as to dispel any
rumours the two of you are connected.
Only problem is you do not get the message. If fact you think
the reverse. That is because you are hopeful.
You want her to tell you off directly?