I think short hair, if done right, can make a woman look great. Not only that but the confidence boost it can give a woman who can pull it off is tremendous. I've seen some very pretty women with short hair, although they were biological female. I'm sure a transgirl could pull off short hair too they will just need to play around with the different hair styles and find one that is suited to them. In my personal opinion any female that decides to cut off their hair and still has that confidence is extremely sexy. Shows she is not afraid of trying different things and is comfortable with herself.
On that note, I'm a biological female and I had my hair cut off to about jaw length last winter. I also had it layered but the point is people liked it. I let it grow out then shaved it off into a faux hawk before thanksgiving. Donated to locks of love.

Anyway point is if you go short be sure you like it and rock it! Confidence goes a long way whether your bio female or trans-woman.