This I think is a tricky one. The information for the encryption is in her head, so if we hold up the order of the judge, why do we have the 5th ammendment? I understand there is a physical piece of evidence but the key to that is in her head, which is protected.
I feel like, if they can crack the encryption then it should be evidence, and if not it should not be used against her. It can be argued that this is a slippery slope.