How do you feel when someone doesn't accept your apology?

I babysit my 2 year old grandson at my son and his wife’s house. They came home after school with 4 year old Zoey. My DIL was giving the kids snacks. Zoey asked for a saltine cracker, and Mom gave her one.
Then she asked if she could spray some Ready Whip on the cracker and mom responded ”NO you can’t spray Ready Whip on the cracker!!”
I was really taken aback at that, and at her tone. I stuck my head around the corner and said, “Why not?”
“Because it’s gross!!” she said.
I said, “Well, it’s just an experiment….” and I trailed off. I’m a firm believer in telling kids “yes,” when ever it’s possible.
I got home and got to thinking about it, and I sent her a text that read, “I’m sorry about the cracker Ready Whip thing. I was so surprised that I just blurted it out. I shouldn’t have done that with Zoey there. I’m sorry.”

She sent back, “It’s whatever.” :(