About getting my ex back

She's 19, I'm 18. Four years ago(2011) we broke up as both of us fell for another person. We then date on and off for a few months and we stopped contacting each other. Two years ago(2013), I texted her and tried to chat with her. She will reluctantly reply with things like 'oh' 'k' 'ya' or most of the times she would not reply. She refused to accept my friend request on Facebook and when I ask simple things friends always ask like 'what's up' she will get so mad and we would quarrel. She would quarrel with me over everything that time. I asked her if she still loves me she said NO. Then we stop contacting again, and it lasted for a whole year. Recently, about a week ago, I sent her a Facebook friend request with a short friendly message. She accepted it and now we are chatting and she is different from the previous time. When I ask her things like 'what will you be doing', she would answer me and would also ask back 'and you?'. Before she sleeps she would let me know and she will say goodnight. (Unlike last two years she would suddenly stop and leave the conversation hanging there). She had once told me she knows my exam results. When asked, she said she looked it up from somewhere. We have not quarreled so far. What do you think about this? Not that she had shown any obvious interest in me, but her attitude towards me has changed. Do you think I would have a chance of getting back together with her if I take it slow and easy? Thanks in advance.