8 yr old DEATHLY afraid of dark

My niece is staying with my family and I for the school year( TX to NV). My Parents put her in my room and that bothers me a little. My brother failed to let us know she is DEATHLY afraid of the dark and sleeping by herself... My stepmom already put an LED night light in my room, and they close the closet doors at night. I hate my closet door being closed and I hate night lights. This one is has a LED bulb so it's 5x brighter than the regular lights that give off an orange type light... She's been here for almost 2 weeks and we still have to fight her to go to bed. She keeps me up almost every night with her crying, sleep talk, and constantly opening the door or waking me up to turn the TV on... School starts in 2 in a half weeks... I don't know what to do about this extreme phobia.... HELP?!