Grandma missed granddaughter 1st birthday party.

We had my daughters 1st birthday party on Sunday. All of her immediate family members were there except my mother. Everyone was calling her and texting her to see where she was, no answer from her. My daughters actual birthday was the next day no call or text from my mother that day either then she texts me the day after saying she went on a little trip and did not get back in time for her party. No apologie or anything in text. She didn’t even call her on her birthday to say happy birthday. Should I not be mad? I didn’t respond to her text because I really don’t want to go off so I just didn’t respond now I just got a text from her saying I can’t change that I missed the party. It’s so ridiculous she knew for months when her party was. Am I overreacting?