I met my ex dumper after 4 months breakup

So, 2 days ago me and my ex we were in the same place for the first time since our breakup (4 months ago), a mutual friend was celebrating her birthday and we were together at the same table, place for many hours.

She brought a friend that even the person who had birthday didnt know, entire group didnt know, and I discovered it's a friend of her that also breakup with her boyfriend at the same time she did and she got super close with her, maybe she brought her to not feel "alone".

My thoughts, I was kinda indifferent with her presence because I felt everything for 3 months, suffered a lot, I got dumped with "its me not you" "I want to be alone" out of no where, she never apologized for anything, blocked me and made me villain to everyone.

She was extremely quiet, barely talked at all, she only talked with this girl that nobody knew, her body language was weird, quiet and felt that she was awkward there. She was avoiding me like hell, never looked at my direction and her body was always turning around from mine, which is funny, because one time she said she didnt want to be in same spot as me because I would be with bad mood and probably "destroy" the ambient which I showed her it's a lie, I was laughing, talking a lot, being myself and totally comfortable with her.

Or she was faking really good, but after 4 months seeing her, after 2 years together, it seemed to be she never cared, she never apologized and probably after her reaction, she will never do it.

I'm proud of myself that I handled it nice and was able to be myself and have fun, laugh, talk and enjoy. She was super quiet and brought a random friend for support maybe? But she's the one who claimed that she lost feelings 2 days after breakup but still need a friend support?

I hoped that she maybe would reachout to say sorry, but seeing her after 4 months just made me realize it will never happen, I never had my closure and never will, and that's life.

There was a time that it was only me, my 2 friends, birthday girl, my ex and that friend that she brought, got kinda awkward but I was still talking with everyone but not with them (both avoiding me) until they couldnt take it anymore and left, hard to tell if my presence was bothering, or if she was indifferent, but it was good for me to see her and feel peace of being able to live my life.