Maybe this is where you should trust the opinions of doctors, and psychologists, and trans people themselves?

As research of transgender people has ramped up in the last decade, more and more studies are coming back to show that this is a natural phenomenon. That the brains of MTF transgender folks skew more toward cisgender females, and FTM folks skew more toward cisgender male.

Your comfort level is obviously not something we can change. But self-education can remove the "doubt" that it's healthy for someone to transition. It's not only healthy, it's life-saving and necessary.