So I watched a movie a few years ago, it came out in at least 2008 . It was a horror movie where there were creatures crawling on the ceiling and the only way to fend them off was with light. They could shape shift and the way the mother in the story dies because she trusted the creatures and turned off her light. I can't remember it and I just need to remember the movie.
I don't recall a part with creatures crawling on the ceiling, but the rest of your description seems to fit well with the movie "Darkness" from 2002.
The shapeshifting creatures in the movie are some kind of personification of Darkness and can only kill things if it is completely dark. There is a scene where the mother is alone with the Darkness disguised as her two kids trying to convince her that everything will be alright if she just turns out the lights.