What's up with her always making smart comments?

I am wondering about something. I've known this young girl who just turned 20 for a little over a year now. Recently she has been making smart comments at me. If i say something, do anything, she'll always have something to say about it. At times they are sarcastic comments. Other times they are smart comments. Both showing or hinting that i did something wrong, or could have said something another way..etc etc. Anyways, she always has something to say about what i do, how i think, what i do...what i say. her comments seem very "corrective" in a sense. How come? Why is this? Obviously the possibility to this answer could be anything....but any feed back would help.