As a tall trans woman it used to be pretty hard to find femme shirts that fit well; most such shirts are either too short or too loose for my tastes.
However, Long Tall Sally's selection has been a godsend. There is some crap in there (both in terms of quality and sizing), but most of the stuff I've found flatters my figure really well.
The main disadvantage is that they're based in the UK and I'm in the US, so shipping and returns are expensive and annoying, but it's still been worth it overall.