I don't stutter but I fell in love with a guy who does. We met online, and it's one of the first things he wrote about himself. I thought it, and the way he told me about it, was extremely adorable, and I was also very excited and happy that he trusted me enough to share that and tell me his feelings about it. Overall I basically pretty much died from cuteness overload. So yeah I'd say tell her by text. Give her the chance to process it and to be curious about it and to ask you about it. Be willing to answer questions about what it's like and about how you feel. Realise that it makes you different and hopefully, if she likes you, she'll think that different is fucking cool. I know people who stutter often feel pretty negatively about it, but from the outside not everyone is going to think that it's negative.