my best friend

some time Sometimes I think that my best friend is so strange. I like her but some time sometimes her behavior is not understandable noncomprehensible for me. Once I sat on in my seat, we were doing having some fun. I have two best friends. On this time occasion, there they were both there. We were some joking to around with each other and suddenly my strange friend was become aggressive on because of my joke. She held a pen and hurt hit me over and over on my arm again and again. I also felt aggressive. In beginning I was astonished, but after some time I did react and beat hit her. My other friend was also surprised that I did that. The next morning, my strange friend felt sorry for her behavior and so I forgave her. I asked her what was wrong with you her but she did not answer me. I did not understand that what thing made her so aggressive.