Quoting K[♥ E&C]:" I'm sorry, but you should've just let it be and not told her that he dad lied to her. Making the other parent out to be a bad guy is pretty low. A kid will figure things out for themselves eventually."
I grew up in a household where my mom was constantly belittling my dad and making him out to be this terrible person. Finally, I realized the truth. My mom and I barely have a relationship, 20 years later.
My dad and I? Couldn't be closer.
It wasn't right of him to say it was cancelled, but maybe something came up that they weren't able to go and instead of disappointing your littler girl, he came up with the excuse it was cancelled.