My 8 year old daughter refused to say happy birthday, or acknowledge my wife's birthday. Any advice on how to deal with this?

To clarify the scenario a little more: I come home from work yesterday to my loving family, and when I ask "Hey did you guys say 'Happy Birthday' to mommy?" My wife says "egh", visibly upset but trying to keep her shit together, "and that our 8 year old hasn't and on top of it had been a complete pill all morning while getting ready for school, and resumed her shit behavior when she got home from school."My wife does everything for us, she's a work-from-home Mom, who's developed an e-commerce site from nothing and chose to give up any ambitions of working to make money, instead focusing on having a good family life, being there for all of our kids (we have 4).The daughter in question does struggle with anxiety and was even diagnosed with selective mutism while in preschool and heading into Kindergarten, when things started to open up a bit more. Today in public she is like any other kid. We see the ball of anxiousness at home that she would never let out in public, willingly. She has had some massive meltdowns.While I can try and make some correlation between her anxiety and how she acted yesterday at home, regarding my wife's birthday, it's really hard to swallow this, knowing just how much my wife pours into our kids, especially my 8 year old.How do I/we go about this? My wife wants to just forget it (I know she's super hurt) and move on, but I feel it will affect their relationship very negatively. I talked to my daughter and let her know just how much she hurt her mother's feelings, but I guess she hasn't been at all contrite about it today and continues to display a somewhat arrogant attitude.She is otherwise a super sweet, empathetic kid (weirdly empathetic from a very young age), but seems to just be acting like an asshat to her mother, especially on her birthday. via /r/Parenting http://ift.tt/2wGn4NF