I did tell her the majority view in this forum and that many told me that the operation of the rule is that even if she got copied by someone without her consent and knowledge, both parties would be deemed to have violated the honor code. Personally, I still don't think that is a fair rule, but we will follow the rule to avoid getting caught up in a bad situation in the future.
Giving your work to another shows knowledge that they could copy your work. Your daughter did have knowledge that the other girl had her work because she gave it to her. The other girl did not steal it without your daughter's knowledge. Your daughter knowingly and willingly sent the work to her friend. At that point, she knew or should have known that her friend could copy the work, even if the friend didn't come right out and say that she was planning to copy it.
This situation is different from the situation mentioned in an earlier post where a student had inadvertently lost papers in a hallway and other kids picked them up and copied them. That student had no knowledge that others had his work and did not consent to being copied. I was always taught that when you allow others to see your work, you know or should know that they could copy it.
It is surprising that you as the parent and an adult find this rule so surprising. Good kids can make mistakes, but if my child told me this story, I would have asked her why she gave her homework to the friend in the first place. She should have known that it is wrong to share your work and that both she and her friend are responsible for doing their own work. I think I would sit down with my child and have a good talk about cheating and plagiarism and how important it is to do one's own work.