I agree--declawing is a horrible thing to have happen to you if you are a cat. Unscrupulous veterinarians will often offer a discount if neutering/declawing is done at the same time... Really, it all comes down to money.
I know how you feel, a little... I know it's not the same thing but my mother had my cat (kitten, really) Tiger put to sleep without telling me first, because he had symptomatic FIV... at the time, I was 10 years old and I would have made the same decision she did, had I had time to think about it.
But I didn't have time to think about why it was being done; nor did I get to say good-bye to my cat, and it was only by overhearing my mom phone the vet that she wanted it done, that I found out it had happened at all (my mother likely planned to tell me she had given the cat away)... I think Tiger knew she was dying when Mom first took her to the vet; because the last time I held her, she was purring and washing me as though I were her kitten, despite her obvious illness. The thought of little Tiger dying in a strange place with no familiar people around made it that much worse for me, and likely pretty bad for Tiger too. All I can think is that she really was loved while she was my cat; and that's as much as any feline can ask for...
I think, really, that parents who don't let their children take part in decisions made about their pets are undermining any of those vaunted lessons on "responsibility" that kids are supposed to learn when they have pets, and telling them instead: "Your thoughts don't matter... we'll make the decisions for you, because that pet is our property, no matter how much you love her or how well you take care of her."
Your particular little cat does have an advantage: She has an owner who really wants the best for her. Most declawed cats live happy lives despite their disability.
Obviously, priority number one now is to keep Kitty inside. Outside, she has no defenses against predators and sadistic humans; and if she gets out, she could be in trouble. Keep her collar and license tag (with current phone number) on her at all times, just in case she does get out; that way, it will be known she is an owned cat.
As for the surgeries... you are most likely aware that your cat will be in some pain for a while. Cats react differently to this... some withdraw and hide; others seek out comfort. Whatever your cat does, respect her... if she hides, you can try casually "hanging out" in the same room with her (without trying to make her stop hiding)... depending on the bond you two have, at her young age, she could be comforted by your presence. Don't force yourself on her, though; some cats are innately comforted by quiet and solitude, and maybe yours is one of those.
Also, make sure she's getting enough water, and that she starts eating decently again within a day or so. (Some cats start eating right away, after the anesthesia wears off; when I had a female cat spayed, she turned up her nose at the kitty food after just a bite or two for about 36 hours, then slowly started eating again. I imagine she just didn't have much appetite.) Soft music can help de-stress some cats; others like the sound of human voices from a radio or TV.
Regarding litter boxes: Most likely, it will hurt her to scratch in a litter box for a while... Many cats will use a litter box after declawing regardless; but if she does not, bear with her, possibly confine her to a room where the floor is easily cleaned (and stay with her as much as possible)... after her paws heal she may need to be assured that she can use the litter box again without it hurting her. Oh, and make sure you have the right kind of litter for her (paper, light pellets, etc.) for a couple weeks after, since normal litter can really irritate recently-declawed paws.
There are also quite a few products designed to make the air smell comforting to a cat... I don't know much about them quite yet but I've heard folks talk about them here, and they seem to work for some if not all cats.