It seems like a good thing to do. BUT don’t make some big fucking deal about it. Just make a joke out of it. Don’t be like “So, there’s something I have to tell you about me...” Fuck that. Just be like “So I just had the most awkward experience. Someone asked for my last name, and I have a pretty moderate stutter. When I tried to say my last name it just wouldn’t come out so this guy thought I forgot my last name. Oof.” Maybe she’ll laugh about it. If she changes how she acts toward you then it wasn’t meant to be anyway. I stutter and my wife doesn’t give a shit. Find someone who will see past it. This is a good test. But, again, don’t be weird about it. Because it’s NOT something to make a big deal about.