Blue note Puns

My Dad and I chat online almost everyday, out of the blue one afternoon I get:

Dad: I came home after work last night and saw a note your Mother left on the refridgerator. "It's not working, I can't take it anymore, I've gone to stay at my Sister's!"

<long pause>

Me: ...?

Dad: I opened the fridge, the light came on and the beer was cold... "WTF was she talkin about??!!