Okay, the ideas below I think would be fantabulous if she were older, so I'm leaving them here because she will be 10 or 12 eventually, but ETA bit is more on topic to your actual situation:
My vote is to direct her to some open-ended design-based projects. Help her brain storm something to make and then let her work out how to do it.
I'm speaking as a person who pretty much breezed through nearly all of a degree in technology and then died in the final project class because I didn't know what to do without instruction.
I LOVED worksheets as a kid. And trivia questions. Things where the question is obvious and all you have to do is write a short answer.
Ooh, there's another good idea, get her to write a paper. You can send her to http://owl.english.purdue.edu/
help allay worries she has that she's doing it wrong. Okay, she might not feel like she's doing it wrong, but it sounds like she's got at least a bit of the sort of perfectionist tendencies that will result in her not caring that you said anything is okay and that she should just write enough to share what she has learned.
Oooo, she wants to learn another language? http://www.livemocha.com/
With the caveat that if she's using only that program she should first learn the alphabet for the language she wants to learn. I tried learning Hindi with it, and got stuck in Lesson one because I couldn't do the reading outloud section.
I asked to go to school as a kid because I knew my mom would make me actually work to learn things, by saying stuff like "oh that sounds interesting, do you need a ride to the library?," while school would let me just get my time in and get credit. Being told what to do was soooo much easier.
If you figure out how to help your dd get over this, be sure to share it so I can fix myself? Thank you!
ETA: oh, she's 6, not 16.
Well, I wasn't quite 5 when I decided to go to school because I knew it'd be easier.
But a 6 year old wanting mama right there as she does stuff is less odd. Is she getting plenty of alone time with you? Can you set up some activities that appeal to all 3 children? Or when you do stuff for her, make them things that'd appeal to your 4 year olds as well?