How do I defending against a protection order?

In this day and age, you actually have options.  Most of your transactions were electronic.  Seek out a forensic electronic expert to review your devices to prove that (1) your contact via your devices with your ex were limited and (2) that she did not reply.  You can and should also contact your phone service provider for copies of your recent bills to show the limited number of texts/calls to your ex... and to show the lack of a reply by her.  You need to get on this part asap as most protective order hearings are usually held fairly quickly after an application is filed.
If you need more time to have the devices processed, then you can ask for a continuance.... but you should really have an attorney assist you in obtaining a continuance so that you don't accidentally make any statements that will implicate you later.
It does sound like your ex is using this as a reverse form of harrassment.  However, it is still a serious allegation to deal with.  Until you go to court, have no additional contact with her.  If she's gone to this extreme, the next step is a charge for witness tampering.... do not risk it.  Instead, invest the funds to prove your innocence, ask the court to have her devices forensically tested, and then seek contempt and attorney's fees from her for a false filing.