cockatiels are know to have night frights, by leaving a light on near by will help some. I leave a 25 watt bulb on the opposite side of the room and have 5 watt light bulb near their cages. I cover my birds at night with dark sheets or blankets so that it eliminates any bright lights from outside getting into their line of vision. you only need to cover 3 sides of the cage leaving the back open. not everybody agrees with covering their cages, by I think it helps a lot.
let's start by getting her in routine that she gets up by 9 am (or when ever you get up) and goes to bed at 9 pm, every day. like I said birds need 12+ hours of sleep to be at their very best. also seeds are fine for part of the diet, but let's try to get a good pellet mix in with the seeds, something like Roudybush or Lafabers. also try to get some veggies in daily or a mash. millet is fine for treats once in a while. also try to take some of the sunflower seeds out of the seed mixture, a few are fine but they get addicted to them and that all they will eat. save them in jar or ice cream bucket as treats. veggies are the easy part of the deal, sweet potatoes mashed with little cinnamon 1/8 of teaspoon to entire mashed up sweet potato. you can freeze part of the mash in snack size zip lock baggies, fresh greens such as endive, parsley, carrot tops, broccoli, chard, romaine, beet greens. here is chop chart that will help you to good choices in veggies and fruit for your bird.
I also give my birds soaked and sprouted grains daily. here is another chart that will help you also.
remember that the above should not be left in the cage for more then couple of hours (2) and should be thrown away the uneaten portion. there are mixes out on the market that you can buy that they really love Worldly Cuisines is one of my birds favorite mashes. you make it up and let it cool and give about 12 to 18 grams. Do you have gram scale? if not a little over a teaspoon to teaspoon and half. I warm mine up in the microwave about 30 seconds from the frig. this is their breakfast in the morning and they get a warm chop at night. (I plant a garden for my birds so I know what they are getting is fresh and healthy with no pesticides, herbicides sprayed on their veggies) if you buy veggies and fruit from the supermarket, you must wash them very well b/4 feeding them to your bird. and what
@Tiel Feathers said baby steps, little tiny, baby steps. i'm working thru that right now with Bebe. he is just now trusting me enough to allow me to feed him little treats thru the bars of his cage.
hope this helps you.