Is NOBODY wrong in the post ? POST : Preface, I am Vietnamese and when the infant is 1 month his/her family will host a small party to celebrate it. 

My cousin, who I am really close with, is the mother of my nephew. She asked me a few weeks ago to do a photoshoot session with my nephew ( I just like to take photos and create scenes, I am not that good at photography anyway). I happily agreed and bought 2 cute bodysuits for the baby to wear to take photos. Her birthday was also a few days ago and I even asked her what she liked and bought it for her. 

Now yesterday was the day my nephew turned 1 month old, and my cousin's family hosted a party. My cousin talked to me all day yesterday, but somehow it *slipped* her mind to mention the party to me. It was only later last night after my dad came home from the party that he mentioned all the other relatives were asking where I was. I asked my cousin why everyone asked about me, and she replied she wasn't attending the party, she was upstairs with the baby the whole time. 

I didn't confront her, but I was and am still upset that my cousin didn't at least mention the party, let alone she didn't even invite me, yet she asked me to spend my time to take photos for her baby ( I also took photos for her pre wedding album and didn't get paid except for them inviting me out for dinner). So I told her I am now busy on the day of the photoshoot ( even though I am not busy). 

So Redditors, Am I the Asshole for feeling upset and not doing what I promised to do?