Well, You have to be brave, And when you come out,
This doesn't mean you love them any less than before, You're just telling them who they've been living with for the past days
You're letting them know that you trust them enough to tell them, That's a big step
Plus she's you mother, There's a high chance she wont go berserk
How about this?
"Mom, I really love very much, I trust you enough to let me tell you this, I'm trans."