Why does my ex act strange?

It just means she wanna show her attitude and make you and her friends feel as if she don't need you anymore but you still go behind her.So its better ask her directly whatever you feel or just stop speaking to her.Even if she wants to speak or stay in touch tell her that you no more want to do it.Just tell her frankly that you don't want anyone who don't respect you.Don't reply her mail.Just bother her least.All the very best!!!!!!!!!!!!!