Another approach might be to ask her about it. Not right at the start of the date, but 20-30 mins or so into it - whenever it feels natural. Ask how she wants you to act when she stutters. Ask if she would ever want you to finish her sentences or if she just wants you to be patient and let her get it out. Ask what she struggles with the most. Make it a talking point; make it something that can help you to build a connection with her. I've never been upset or offended by someone showing genuine interest in my stutter and how it affects my day to day life.