Abusive Buyers

Hi

I would like to know why we cannot leave negative feedback for buyers.  I received a message from a buyer who said  "This item hasn't arrived. If it doesn't arrive soon I will be be opening up a dispute against you.  I am over Ebay sellers not sending my purchased items".  I sent the item on 29th December. I hadn't heard anything until today so assumed she received it. I didn't have tracking because I sell a lot of items only worth a few dollars and parcel rate with tracking is out of the question. I messaged her saying I could resend the item or refund the total amount.  She hasn't replied.   So my question is if I have tried to do the right thing in offering to resend it or refund it, and she just doesn't reply and leaves me negative feedback, why shouldn't I be able to leave her the same if I have tried to resolve the situation.

Thanks