I had a similar experience this summer with my friend.
We have known each other since 5th grade and we were close. When we were kids we had similar temperaments but as we got over, she got more outgoing and sanguinc /choleric while I changed to be more phlegmatic with anxiety which was caused both by genetics and external reasons.
We only saw each other once a week or so because both of us went to other towns but we still had a lot in common, sharing our secrets together, going for walks, swimming when we got a chance. When she was with me, she was really very OK and calm, but she talked about the hysterical scenes that she made to her boyfriends and she laughed how she humiliated them. I found it strange and often times I was on the boys side, but I thought it was something she would only do to a boy.
But only after I think about it in retrospective, I've learned very fast to not speak about my different opinions with her. I was always submissive to her. But I still considered her to be a good friend, and she was definitely the only friend I had in this area.
This summer we spent a holiday together and our opposite temperaments fully showed up. I will not say whose fault it was because I made mistakes too.
I was really anxious in a new environment with a few panic attacks which she didn't understand and accused me of being boring and weird. There was also another person who likes humiliating others so they played a few jokes on me, trying to put me down and to "see how I will react". The were things such as trying to forcefully unbottom my shirt in the pub (they only had one beer). Than when I was having a shower they hid the shirt and I never found it again. They did it because the shirt was too modest and they wanted me to show my decolt. They also took my phone and tried to put a picture of penis on my fb. And similar things all the time. They behaved like 13 yo bullies.
I couldn't wait to get home. After the return I received a long mail from this girl where she wrote about all my negative characteristics and how I disappointed her etc.
I learned that even if someone appears to behave kindly to you, but you see them being cruel to others, as my friend talked about hurting her boyfriend, be sure they will behave the same way to you one day.