I wouldn't call that paranoia. paranoia is when you believe that people are either out to get you or following you or talking about you.

It can range from stuff that could happen, to stuff that is really not likely to happen.

If you are sitting there thinking about your neighbors wanting to poison you, that would be paranoia.

I think what you experienced was irritation and anger and justified because of the pain you were in. Not sure about following her all the way to Wal-Mart, but I am glad you left before it escalated.

I hope you are feeling better.