Ugg...that is not good.
Have you tried emailing her through her Paypal address that was provided when you made payment?
It's surprising that she kept great communication and then would not send the item out. But like I mentioned above try emailing her through her Paypal address. I would also try and email her through ebay again, so you cover your bases.
I don't know if it would help but you could call ebay too and ask what can be done since it is past the 90 days.