Don't know if your DD same/same my DD but these have been my winners:
1)Desk toys: from bb magnets, sculptures, spinning tops, all that stuff....... (as I understand it) rooms are a sanctuary right now. It's a spot where she can relax a little or sit and talk to another mid/plebe. My own DD told me that every little gizmo "toy" I sent to her was picked up by other mids when they visited her room. They were passed around-fiddled with-laughed about by plebes/mids that just wanted to "chill" and BS for a while. Magnets were perfect for this. Some of the ones we sent made it out to the "watch desk" where I assume they helped multiple plebes in her company pass an hour or two. NOTE, DO NOT send a 80 lb.force rare earth magnet----apparently it really pisses off the base post office.
2) Any cheap toy that can bounce a projectile off the forehead of another Mid.
3) I can't remember if DD asked for it, or DW and I just thought of it, but DD liked the powered blue tooth speaker we gave her for Christmas Plebe year. Do a little research: Google "Bluetooth powered speaker reviews 2019". She can't have the thing turned up loud, so look for something that offers good sound reproduction for a small room, rather than a "party speaker".
4)A year of PANDORA, Apple Music Etc. is a great gift---even if your kid isn't a big music fan. Pandora gives them tunes they can stream to that speaker or her phone and listen to while she runs or works out.
5) Staying with #4; a good set of blue tooth capable earbuds. Not "IPods" ones that will stay in her ears while she runs (they all run). Here again "google is your friend"--- an evil friend but use them to find ones that are well-reviewed and work with her phone.
6) Insoles: If she doesn't already have them, find a sporting goods store that specializes in running, and get her a gift-cert for a pair of custom insoles for her shoes. You may get a "WT-?" look on Christmas day, but MAKE HER go and get them done over Christmas break. Running, or standing in formation, she'll get it. If cash is an issue you can take her to Big5 or find a Dr. Schols eval platform and buy the ones that fit best.
7) Personal favorite a 2nd pair of sunglasses. They all have their RayBans, but when you think about it, a different pair of sunglasses is really the only thing a Mid can change in their day-to-day Uniform. Our DD has really enjoyed and gotten a lot of use out of sunglasses that include a lighter tinting, or gradient, or photochromatic, or a rose/sedona lens for high overcasts days. You can go anywhere from $300+ for a pair of photo-k vintage real glass Italian made raybans to a $50 pair of Oakley Tailhooks (won't last forever, but good optics and they look sharp). Just grab something that changes things up a bit for her; square vs round or acetate frames vs wire.
8) Art from home, something from a local art fair that depicts "home". A framed picture of her with the family dog. Something she associates with you, mom, grandma, etc. (Keep it small)
There you go. No way to know if your DD is anything like mine, but these are things our DD has enjoyed over her years at USNA.
Good luck