What are these girls behavior?

So there are a few things i need some clarification / explanation i need from you guys about this one girl's behaviors who happened to be my ex girlfriend. We broke up 6 months ago but there are things that still annoy me till today.

1/ She had a new relationship 1 week after the break up, with the guy she told me that "he's just a friend" and how much she hates him coz he's so annoying and acting like a child and creepy. Is it possible that she's been cheating on me with this guy the whole time?

2/ We worked for the same company and she always told me how much she hates these girls, that guy in the workplace, but after breaking up with me (I didn't work for that company anymore) she acted like she never really hates them from the beginning and do stuffs like: like their social media stuffs, hanging out and having fun etc. I felt like i was being lied to and she was like a completely different person that i knew.

3/ She was talking sh*t about me with her bff through texting and i accidentally found out because I was holding her phone and the text came in, she was like jumping over and grab the phone away from me and trying to hide it. I called her out on her bs about why would she did that, if there are anything all she need is just talk to me and communicate like 2 grown ass people. She tried to distract to what i had to say and drive the convo away to different topic. how do i deal with this? Is it that I treated her with respect the whole time and she got bored of me being respectful or what?
What are these girls behavior?
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