Would you still be nice to someone who had hurt your close friend

I am wondering if I am being childish because every time anyone hurts someone that I care about I get really defensive for that person and I find it hard to be nice to that person who has hurt him/her.

But as far as I know no one has done that for me, like it was my birthday last week and being an introvert I wanted to have a nice quite movie time together but she ruined it by lying to me and playing the victim, we waited 1 hour for her to come and before that we had called her many times which she didn’t answer. she was blaming me for her being hungry ( she said it was because she came she didn’t get a chance to eat and That she was dying of hunger)

Here, I thought he was going to stand up for me but he said nothing and he is the type that always talks up if it doesn’t go according to what he likes

But I thought I should just let it be and tried talking to her which she ignores

While she kept on talking to my bf and was laughing with him. ( I was sitting between both of them)

And when we went back since our road back was the same she came with us ... and she was literally talking about things I couldn’t talk about and I became very sad.

That night I ended up crying and talked to bf about how I didn’t like how she was behaving with him

But till now when I am with him, she calls him and they talk so nicely and he advertises her products on the internet

I am sorry for this long post

I know it is confusing

I was just wondering won’t he be mad at her or the least not be so nice to her after what she has done

Or am I being immature