^^ I agree. She's probably saying to herself "I bet I can get this guy to IM me even though I broke with him." Hell, she's probably making a bet with her friends she can get you to crawl back to her. And guess what? Once you do, she will be rude as hell again! Right now, she has power over you because you're letting her have power over you. Be a man and say enough is enough and delete her from your life.
And believe me, I have the same problems with this. I tended to read between the lines all the time! And guess where it led me? NOWHERE! In fact, it probably screwed me over even more than any break up ever did. Don't sulk about it. Don't say to yourself, "maybe there's a chance we can get back together." Guess what? There's no chance!
Who has everything to gain from this? HER! Who has everything to lose from this? YOU! She wants you to read a lot into it. Hell, she's counting on it. Why else would she be playing that stuff?
If you're going to fall for this you might as well pull your heart out of your chest and give it to her on a silver platter.
Now, don't worry, don't fret, and go live your life without her.
I will do my best to reply with an educated, humble and honest answer. Ultimately, it is up to you whether you want to listen to my advice or ignore it completely. Sometimes, my advice may be wrong; occasionally, it will be right. Regardless, I want to do my best to give people answers they are seeking.