Hi,
I don't know if you are going to be able to convince your mom of anything. If she is uncomfortable with your father's transition then she may be projecting her uncomfortableness with the change on to you. Or she may feel that she is left out as the one who is uncomfortable and that her thinking and saying that you are uncomfortable makes her feel like she has someone on her "side". I don't know how old you were when your parents got divorced, but I know that when my parents fought and from talking to my friends that parents can try and get their children to side with them on any and every issue. Does she try to get you to agree with her against what your dad says on other issues or just this issue? I know my mom would always try to get me to side against my dad. Good luck.