Sara, I'd like to propose a different scenario.
When you first asked if you could try on the outfit, the SA likely had NO IDEA that you are TG. You were in guy mode and you hadn't yet showed her your pictures. I know it seems like a no brainer to those of us who hang out here all the time, but believe it or not, most people don't automatically think "TG" when presented with a male who wants to go into the ladies rooms. What comes to mind instead, is the ubiquitous fear that most females experience around potentially unsafe situations involving men, the same fear that makes a woman uneasy about walking out alone at night. Trust me on this. The fear is real, and it is there because of centuries of men having had the upper hand on women physically, psychologically, and legally.
Also, here are some rape statistics: http://www2.ucsc.edu/rape-prevention/statistics.html
91% of victims are female, 9% are male, with 99% of rapists being male. There are good reasons for women feeling uneasy about having men around when they are undressing. And how many times have there been comments in this very forum from CDs saying they don't like being around men because most of themare pigsdisrespect women? And again, most female customers would not immediately consider that the male in the dressing rooms is TG and therefore is not a physical threat.
When the SA realized that you did have a legit reason to use the rooms, she offered you the opportunity. It would have been nice of you to take advantage of it. Maybe next time, you could explain that you are TG and show her the pics before asking to try on an outfit.
I seriously doubt that most women would feel comfortable entering men's changing areas. I've shopped for clothing with my sons for years, and I waited outside for them to come out and show me how the clothes fit. I've seen other women wait outside too. I've also seen women bring male clothing in the women's rooms on very rare occasions. And besides, women haven't historically been a physical threat to men like the reverse, so on the off chance a woman should walk into the male dressing room, I seriously doubt the male would fear for his safety.
Liz ... you could not be more wrong about this. Have you read all the threads in the F2M forum here? It's not a picnic for them either.