When we first got Socks, we got her declawed too. Don't worry...I'm not going to flame you, and I hope no one flames me. I honestly didn't know what it puts the kitties through but now I know better. Anyway, understandably, Socks had some discomfort and developed quirky little habits like your Pixel (who is beautiful, btw!).
As I remember it (I was only nine years old...), Socks did something quite similar but she eventually stopped doing it. We had to use newspaper in the box, and we brought in some grass to mix with it to make it a little more natural for her (she was a barncat at first). We did this for the first year that she was declawed, as we were unsure how long we should do it. Our vet told us to use regular litter and let her "get used to it", but we just couldn't do that.
We don't know if Socks has any permanent damage, though I'm sure she probably does. She doesn't appear to be in pain somedays, but she seems to have "phantom pain" or something, where she will just sit kind of like your Pixel does and stare down, looking like she's staring at her feet. And it's been nearly nine years.
If someone cut my fingers off, I would probably refrain from using my hands for a while. That's probably what Pixel is doing.
Please, if you get another kitty, please consider not declawing. There is a world of other alternatives out there...Softpaws, scratching posts, etc. Please just consider it... what's done to Pixel is done, and I don't blame you for that, having done the same thing myself. However, please look into the matter further if and when you ever get another cat. Thank you.