Awe, I'm so sorry Shery, it's not your fault at all. This happens quite often to people who are new bird owners, they take their bird into an Exotic's Vet for "grooming", thinking that it's necessary for their health and well-being, like you do with a dog or a cat, and they end up with all kinds of issues and often tragedy. I've seen this happen before with beaks being ground-down, wings being clipped down to literally nothing, where the Exotic Vet takes all of their Primary and Secondary wings and the bird has nothing but stubs left, and it takes over a year for them to grow back, sometimes they don't ever grow back because they damage the follicles...I've seen toenails cut down to the skin of the toe...It's horrible. But it's not your fault, you're not the Veterinarian that should know better, or not be doing it if they don't...
Make sure you're checking her feet every single day, multiple times a day for swelling, puffiness, redness, bleeding, or any sign of an abscess/lump forming anywhere, both on top and on the bottom, and on all toes. Try to keep her cage/perches ultra clean for a while, scrubbing all of the poop off of anywhere she stands daily, so as to prevent infection...
****She is definitely stressed, and this is absolutely playing a part in her lethargy, sleepiness, and her attitude. However, since this Vet clipped all 8 of her toenails right down to nothing and let the veins bleed, she also most-likely lost a ton of blood, and with such a small bird, she is probably also Anemic. Keep an eye on her color, specifically the color of her beak, and if you see it looking at all gray or blue in color, then she is very Anemic and needs to get to a CAV immediately. In the meantime, it's very important that she's eating and drinking as much as possible. Now is the time to spoil her with sugary fresh fruit, as it will provide her with lots of hydration, and it will keep her blood sugar up. She needs lots of fluids, so fresh fruit such as apples, grapes, anything else that she likes is a really good idea. Also, even though you should not regularly give your birds citrus fruit because it enhances their absorption of iron, and birds can suffer from Iron Storage Syndrome if they absorb too much iron, I highly suggest that you give her a bit of orange juice to drink each day until she's feeling better. They usually love it, it's how I give my guys any medications they have to take orally. I just pour a little in the cap of the orange juice carton, and they drink it right out of the cap...She will benefit from the hydration, the sugar, and right now, the iron because she is definitely Anemic...You can also buy a container of unflavored Pedialyte or the generic store-brand of the same thing, and mix it half-and-half with her drinking water each day, that will get some electrolytes in her...
Keep us posted...I'm honestly not surprised she's still kind of gutted after 3 days, as they don't have that kind of blood to lose, they aren't like dogs or cats, and Exotic's Vets just don't get it. So not only did she lose a ton of fluids, she lost a ton of red blood cells, and it takes time for them to be replaced; that's why the extra hydration, sugar, etc. is so important. The little bit of orange juice once or twice daily for the next couple of days should make her feel better pretty quickly...