I don't know what to say about the other things, but that pings pretty strongly as an discrimination of some kind to say you can't use EITHER bathroom. I think if you somehow had proof of their actions you might have a legal case about it...Well, most of all, are you still with a therapist? He/she might have a pretty good idea about what you can do about this, because I think it does count as a discrimination to enforce your original provided name&gender alone...
I dunno. I really feel you should take the initiative, because it's not really that great of work security for them to suddenly treat you badly like this... :S
Another thing, I'm pretty surprised the girl is saying that Oo; I would've figured any transgender would not say such a thing as 'male because of what you have'...it's kind of the line of thought we fight against just to realize what we want, right...? o.o;