Did I miss something???

It all started at my son's 4th birthday party April 25th, my son's celebration took place in my backyard, he had a bouncy slide and BBQ. My friend's 6 year old son runs over to me crying saying Izzy is not my friend, so I call my son over tell him not to be mean to his friends, he apologizes and they go back to playing (I did not think to ask why he said this to his friend I just corrected him). Okay so hours later...I mean the party was over my friend (the mother of the boy) asks me is everything cool. At first I really had no clue what she is referring to, so I am like I don't know what you are asking. She briefly refers to the boy's tat so I reply oh "yeah, I guess I mean Izzy apologized", they have been playing. I hug her, kiss her, and give her little man a kiss on the cheek. OKAY this is were I am sooo lost. My friend comes back later that night holding a gift that I had given to her son, she tells me that She loves me and my family but cannot be mistreated and can't be in my life anymore.....ooookay. I ask her where is all this coming from she says she spoke with her son and he said that Izzy had said some really mean things, She leaves. I ask my son what happened he tells me that he told the boy the things he did because the boy kept trying to push him down the bounce slide and he did not like it. The mean things said by him was -I am not your friend anymore, and I don't want to play with you- I contact her right away with hopes to get better understanding of the whole thing...she responds to me saying that me telling her this is to justify my child's mean behavior and that I am not only vague but misleading in my response. Se say's that my child should have chosen different words. I tell her that her rules to life do not apply to my 4 year old child (Botton line he had been corrected from jump and had already apolpgized).

Okay now I am no longer concerned...nor confused, now I am pissed

This ends with me telling her some things that I will not take back. I am shocked that this whole thing went this far.

Why did she wait the entire party to ask about the problem?
Why did she ask ME if everything was cool instead of the children?

I sill want to know How I was being vague and misleading.
We are no longer friends.