I’m so happy to hear that she is doing better! 
I don’t think you were too worried, bunnies are very fragile (even adult ones), and hide their symptoms well, and sometimes act normal until it’s an emergency, so you were right to seek help!
About the veggies, it’s true that young bunnies shouldn’t have veggies yet, and usually you want to introduce them very slowly, one at a time. I haven’t heard of feeding rabbits horseradish, do you mean the green tops? That would make sense, as it’s in the same group of veggies as radish, kale, arugula, bok choy, cabbage. Some of veggies (cabbage especially) can cause gas, so it’s best to only give a little at first to see how your bunny reacts to it.
If she tolerated the horseradish greens well, I think it would be OK to continue giving it in small amounts. What are the other dried veggies you are thinking of?
I can’t remember, do you have access to hay? Hay is the most important part of a bunnies diet.
I think at this point it is important to keep things very stable for her, and not change too many parts of her diet at once.
.
.
.
The answers provided in this discussion are for general guideline purposes only. The information is not intended to diagnose or treat your pet. Seek the advice of your veterinarian or a qualified behaviorist.