Sorry, I just saw your question Jan. No she definitely couldn't have ate anything toxic, she had only been in her run and I always check it before they go in, and if Pebble had eaten it Ebony would have too - they never ate separately.
Ebony is very sad, she spends a lot of time just laying by herself, I feel so bad for her. She's been getting extra attention and has been in the house a lot more, but it's just not the same. In November hopefully I'll be getting NICs from B&Q, then I'm allowed to have Ebony as an inside rabbit, even if she doesn't bond with Madison (but I'm quite confident that she will).