I woke up from a dream yesterday. In this dream I was a girl, but further into the dream I realized I wasn't a biological girl, I was a fully transitioned MTF. I was grocery shopping, and this woman was following me around the store, harrassing me and making fun of me for being trans. Why would I have a dream like this?

I didn't know whether to put this in transgender or transsexual talk, so sorry if its in the wrong board.

It most likely is the nagging little voice of past training.  It also can help with what was not quite right.

maybe you had a premonition. 

Seems like you're just concerned that you won't be accepted especially by women. A valid concern we all have at one point or another.