So my sister is the only one who knows that I'm Transgender. The thing is, she is threatening to tell my mum. She doesn't understand what it is like for me, and that my mum is filled with worry, because there is something wrong with my brother's unborn baby. She won't let me tell my mum in my own time, when I feel the time is right to tell her, and makes me worried that when I'm not around, she will tell her. Do I tell my mum now, or wait?