When speaking to a person for the first time, I bring it up once I feel I had a noticeable block or stutter. I just say something like, "you might not know this about me, but I stutter." Then we just move on. As for relaxing, what happens to me is the more I talk to someone and spend time with them, the more comfortable I am with them. Assuming you're over 20, I don't think she'll have a problem with stuttering. I rarely meet people who do, but if she does, remember she isn't worth your time. Good luck!