I see your point. However, there are many ways she could have done, without the weight being put on her mom, which I think was her heart. Perhaps in future it could be something like:
I understand mom, you're in a difficult position. I love you, and Mother's Day is about you... so, though I'm sad I won't get to see you on such a special day, I will honor your request.
That way no fibbing is involved, no one else is getting socked, and the drama is kept to a minimum. This all assumes that Rhonda didn't want to put this on mom... at least for that day.
Just some further thoughts...LGF