If you're having a lazy day at home and you want to spend the day in PJs... do you fix your hair all nice and put on makeup or do you just lounge about all warm and comfy in your PJs?
Let the girl have her PJs, be warm and snuggly and maybe look a little silly, (in YOUR opinion, she could never look silly to me), and leave her hair alone!
Seriously though, I'm sure a little over spill of hair can't look that bad enough to give her hair a trim. I demand photographic evidence.