probably withdrawal symptoms post Christmas coziness, so do try to give her a bit of extra attention to make up for the difference.
a soft nightlight will help with fear of dark - if it is a real thing, but if she just uses that as an excuse to be with you, than not the solution (though still reassuring).
you could try this - she has to stay in bed all night for the school nights (sticker if she did), if she does well she can sleep on her mattress on the floor next to your bed on Friday or Saturday night as a treat.
(mine do that anyway if ill or scared or wet the bed, so we have an extra cot mattress with a cover ready to use)
if on the other hand you don't want her to get in to your bed/bedroom ask her what it is in dark she is afraid of?
I heard this story, thought was fab : kid was afraid of the dark, coz of imaginary wolves coming to eat her, so dad helped her make a wolf-zapper out of an old plastic bottle, which she kept next to her pillow just in case. no point telling there are no wolves, to her they were realm, so needed a real solution!
mine used to be afraid of crocodiles, so I'd stand at the window and shout - "go away crocs, back to the Nile!" then we'd giggle at how scared the crocs were of mummy and they'd point at the shadows look mummy, there's one running away! (then back to bed, safe from predators!)
what do you think?