I don't understand her!

Just to breeze through,this was what happened.
This girl was in my class.We got along like any normal classmate.We were on both each other's FB,but not on IM.
This happened around 5 months back.
One day,I suddenly,casually and jokingly told her what was said about her.Realising her facial expression changed,i asked her nicely if she was angry.She said no.
Wanting to make sure I wasn't taking things for granted,I sent her a PM on FB.No reply.
Following this,we never once talked in the class.
Soon,i realised she del me off her FB.To be specific,she deleted me off 2 months after the incident.
All along thought,i caught her looking at me with a subtle soft look[one that is neither aggressive nor threatening]
She never skipped class halfway.However,once,a rather attratice female friend came to delivery me lunch,and within a minute,she packed her bag and left.

One month ago,the term ended.I approached her in an attempt to make good.I asked if she was still on that matter,and she said no.
The following day,she added me on IM[but never online]

A month later after she added me on IM...
Read on...

Now,for more than a month,up until today,I've been wrestling my thoughts,mentally enacting her responding behaviours towards me-factoring in all very possible reasons as to why someone would act in such manner-taking the stance of two opponent on the cheeseboard:deconstructing and stripping the 'whys' to its very bare naked essence.

Deconstructing her entire complex model of behaviour,which is supposed to bring my inquisition over the answer of her root actions,instead leads to what I call "a track that ends in the middle of nowhere"
This mental fiscal has proved to be perplexing,extremely futile,and supperfluosly convoluted,but yet seeking an answer to such an erractic and spontaneous behaviour spruce me.

It,to me,has become the normality to playing maytr to 'social ritual games' of romantice pursuers.But this,one whom hasn't obviously outwardly display any form of affections or interests from my point of logical view[although more experienced female friends have concluded she holds an interest for me,but doesn't yet know how to react to her circumstances given her complicated r/s,or for other reasons unknown due to the lack of a precise model to exemplify]

The question lies herein-

Ever since then-which has been alittle more than a month-she never came online[I've been frequently on IM since I'm helping out with the admin work at uncle's office]
Yet so,it appears that she has been rather active on facebook[as seen from her active comments to our mutal friends]
Early last week,to further my goodwill gesture in the form of a well-intention,I added her on FB[since she del me over the whole apparent incident].
Today,whilst browsing through my homepage,She made a comment to our mutal friend.Now,the thing is;her current DP is different from the one she had at the point of time I added her last week.So-it would seem-she has been online[of course,the verdict is open to the possibilities of her not entertaining her list friend's request]

Since she added me on IM the next day,following my 'interaction' the previous day,it should be pressumed[tell me if I'm wrong] she added me as a goodwill,as an opportunity in context of social ritual,to make up.
Then why,is she behaving in these 'hysterical' manner that appears to entail null reasonings or causes?There seem to lack of a point of references pertaining to whatever that is causing her to act in such a manner-which it is

Try not using Facebook to pick up women and judge what they do based on it :P

Use real life.

seriously, I agree with r4ndom.. don't use facebook and judge what they do based on it.. I mean when my friends add me on facebook, sometimes it would take me a month to approve them because I would always forget to go back and click "approve" after I view their pictures and profiles to make sure that I'm adding my friends and not a total stranger.

also the other time, it was my birthday, and so many people said happy birthdays to me on facebook but I never respond back because there were too many of them and what am I supposed to say? "thanks?" I mean I should but I hardly ever talk to those friends, they wouldn't even know that it's my birthday if it wasn't for facebook.