I don't think she did...or at the very least it's not as open and shut as you present it.
Opinions are generally mixed. I don't think she should have read the statement declaring her innocence.
One major difference between congressional testimony and criminal proceedings is that in the latter instance, you aren't compelled to testify. If she had failed to appear before Congress, she would have been held in contempt. Selective invocation seems appropriate to me in this case.
It would seem that all of this might come down to her being recalled and failing to appear resulting in contempt charges which will provide delicious irony given Rex's earlier thread regarding the two "scoundrels" who stiffed John Conyers' subpoena to appear