If the teacher is Miss Herfirstname . . .

Am I Mrs. Mylastname? I'd feel funny being Miss Myfirstname. I even feel
funny being Mrs. Mylastname. It's so formal. I like being Myfirstname, but
that's too informal, if I have to call the teacher Miss Herfirstname, which
I figure I have to, since she introduced herself that way. What is the best
way to introduce myself to a teacher who introduces herself as Miss
Herfirstname? This happens so much, I never know what to do. I just say my
whole name, but I'd rather figure out what I'm most comfy with, so I'd like
to know what other people are most comfy with first.