I think the primary problem is that many times people look at TG women and assume that their desire to transition must be related to some mental health disorder. The truth is I have dealt with depression since I was a child, but I never felt in any way that my depression & desire to transition were related. I know some on here have felt that, but not everyone does.
By the way, if anyone is dealing with depression I would suggest you read Lincoln's Melancholy by Joshua Wolf Shenk, & the Noon Day Demon by Andrew Solomon.