Well, she didn't try to kill her. That's the biggest problem with the attempted murder scenario that I see. Would she have? Maybe. But we don't convict people on what they might have done. That would require a degree of mind reading that we don't possess yet. I say, prosecute her to the limit for what she DID do and forget about what you think she might have done.
Actually she did try to kidnap her, and all her supplies indicate premediated murder, so yes she should be charged with attempted murder or, at least conspiracy to murder.