>>/28205/
This is possible, but I think you have to consider how trendy it was in those tumblr communities during that time period to have an 18 bmi for females(and agenders like Ken). If she was willing to go far enough to start going by different pronouns including he/him, say she's pansexual, and adopt the entire generic tumblr persona, why wouldn't she adopt the bmi too?

Also you could still be right, but Google what age women stop growing. They reach their adult height by 14-15 whereas a male would possibly still be gaining height at 17. At least you had a reason to think you might be taller. Its more than likely she knew her height and knew she was done growing too.