I don't think I've told many (if any) people that I stutter. It is obvious to me. That said, I don't blame you for not telling her. I do think you should tell her to gauge her reaction from her about how she feels about people who stutter. Imagine if she was laughing at some other physical or mental disability. Why should it matter if she can't tell you stutter or not? I had someone recently laugh in my face when I introduced myself, and it boiled my blood. This was a stranger and has built up resentment on my end as a result. If you tell her and she laughs or mocks you for it, then I would leave or have her educated on why people stutter. I don't get out much because of my stuttering, but I don't think I could ever be in a relationship, romantic or otherwise, where the person in question would laugh at something I can't control and can't be rid of.