What can I do about being harassed by emails?

I am being harassed by a woman who is unhappy with Sugar Gliders I sold her. We were away from our house on a 96. A 96 is where you get free days off work in the military for holidays which is where I work. She got mad because she called us while we were away from our home to ask information about the gliders (mainly the lineage) and we did not know it off the top of our heads. We also were not going to dive all the way home to get it for her at that moment. We told her we would give it to here once we got home. The information was on the computer. We got home really late that night and went to bed. The next morning we awoke to find a really nasty email from her. She was being really rude and nasty. This all happened within a day. She waited a day. We then refused to help her. We told her why. We told her to stop emailing us and cease all contact. We even blocked her email. We also told her if she was unhappy with the gliders we would give her the money back in exchange for the sugar babies. Plus she seemed a bit fruity and we felt bad having sold them to her after we got the email.

She created new emails and started sending us emails. She refuses to give the gliders back in exchange for the money she spent. She gets ugly and threatening. She also is saying she is taking us to court. For what I don't know because none of this makes any sense. She also said she was going to spread lies about us on our glider forum so no one will buy from us. I have all her emails and everything. She is still emailing us. We live in NC. Is there anything we can do legally to get her to leave us alone?