Just a few points:
1. As others have said, stop using the night light. Having consistently high temperatures and light 24/7 will mess with her circadian rhythm, hormone production, metabolism, etc and also cause dehydration. She could be sleeping so much because she's exhausted, and since she has no natural day and night cycle (from the 24/7 lighting) her body has no idea when to sleep naturally, so she just passes out when she gets too tired. Bearded Dragons do not need heat at night unless enclosure temperatures fall below 65. They need the dark and cooler temperatures to allow their bodies to rest and recuperate from the intense heat and light of the day. If you need night heating, use a ceramic heat emitter. They emit heat but no light. They can also last 1-5 years, so are better for your wallet and the environment because you don't have to replace them every 1-3 months like with incandescent bulbs, which produces less waste.
2. As for eating, what do you feed her, how often, and how much does she eat? A 2 year old dragon would be considered an adult and protein intake should be cut down to every 2-3 days. Having high protein meals every day and not eating any greens whatsoever can cause gout, which is extremely painful. Decreasing feeding her insects to every 2-3 days should also make her hungrier and more willing to eat salads. Usually after they try the salads, they realize they do actually like them some. A few weeks of feeding my dragon insects every other day made him realized he actually liked salads and he will now eat them on most days. Also try feeding the salad first thing in the morning after she has been basking for about an hour. This way she has to eat her veggies before getting any insects. And try a large variety to see what she likes. My dragon won't touch salads that I top with alfalfa sprouts, but he likes his greens topped with apples or zucchini. It can take a lot of trial and error.
3. I'm definitely glad you are switching substrates. If she's been on sand for 2 years, I would give her a careful exam and feel around her stomach for any hard lumps. Being impacted (full of) sand could also be making her feel lethargic and not want to eat. I, personally, wouldn't recommend the carpet, as it's difficult to clean and bearded dragons have such poor immune systems, you need to clean the poop as soon as possible. They could also get their toe nails caught in it and in general it can be uncomfortable for them to move around on since they have rough scales that catch on the carpet. My dragons hated his carpet and I returned after one day. Tile is much easier to sanitize and is a very attractive and eco friendly option, since it will last beyond the dragons lifetime, again creating less waste in the world and making it so you don't have to buy substrate ever again. You can also use non-stick linoleum, non-stick shelf liner, slate, flagstone, newspaper, and kitchen roll (paper towel). Whatever you choose, make sure it is easy to clean as that will be the most important factor in keeping a healthy dragon.
