Unless this is your first time talking to her ever, she already knows you stutter. Periods of very mild stuttering may seem perfectly fluent to us, but people still notice. I promise you she doesn't care. I've had friends that ask me why I don't talk much and I tell them I have a stutter, the response is usually something along the lines of "yea no duh. Who cares? I still want to hear what you have to say". We're our worst critics. I still go silent occasionally but I'm slowly growing to learn that anybody that can't wait on my speech doesn't deserve my thoughts. Sounds like your friend didn't mention it because she still wants to hear what you have to say.