I don't think the teacher randomly decided to speak to the other parent after the class. I imagine there was a particular reason for it, and she was afraid she would miss the opportunity if she didn't act quickly.  I can understand that she was tired after the class and had other commitments as well.

I'd like to see the LW explaining to the daughter that this wasn't a slight to her, rather than jumping in and treating it as a bigger deal than it was.