Firstly, It's a he not a she. I can see why this dude with breasts and makeup wasn't allowed in. I mean if you're going to have a surgery to become a hybrid of both genders then you have to consider all of the problems you'll face in life. This incident is one of many to come.
It's his own fault.
He isn't trying to be a hybrid. People like this struggle mentally and pysically with their current gender and feel they need to be the other. There are several surgeries involved to complete the process which include:
Extended periods of Phycological evaluation, during which estregen or testosterone is introduced into their system to either grow breast and up the pitch in their voice or lower the pitch and reduce breast size for women who are undergoing the change.
Then there are the surgeries involved to actually make the changes such as changing over the genitalia.
Now I do see where you are coming from with your post. during the process their is a period of Hybrid like qualities. and I do agree if this is just a boy who has yet to begin all of this, then he needs to continue using the men's waiting room until the actual surgery has begun.
Isn't transgender the act of switching genders through surgery? Because from the interview he has not undergone any surgery and is physically still a male and so is just a guy wearing womens clothing so I agree with him not going into the womens restroom and locker room. Now if he had gone through with surgery to become female physically then I wouldn't have a problem with it.
I was wondering this myself actually. I think you have to be 21 before you are actually able to undergo this surgery. And She (he) is a High shchool senior (18yrs old) so your point is validated in this case.
Also if he(she)......

.....has yet to undergo the surgery than he (she) is not transgender but a cross dresser until the surgery is actually being done (which takes several surgeries to complete)
So you have a very good point.