I have the same issue. She won't eat it and has a little voice line above her head about how we should talk about it but there are no options to trigger a conversation.
I had tried it once in act 1 when I got the noblestalk in the first place and it worked but I had reloaded an early save on advice from a friend to help Derryth first and try this in act 3 but now it's not functioning. No additional options.
