Hi! I'm so sorry the beeping is too loud. That sounds like a really bad experience for your wife :(. We have gotten this feedback and are working on making it better.
For the time being you can press the pause/play button to stop it and then just press pay again to keep the water heating. Also you can use an external timer, like your phone or oven. I know this is way less than ideal, but we are working to fix this issue for the future.
I will double check on Monday that there is nothing else that can be done to fix the problem immediately.
Let me know if there is anything else I can help you with.