you need to stand up for yourself, a simple "can you explain what is so funny?" can put that karen in her place. I don't know about your situation or your type of stutter, but for me, being angry literally eliminates my stutter so I love confrontations it is not worth feeling down because some a..hole is being a karen. this is something that is out of your control and only a child would laugh at such a thing. if you don't like confrontation then you should have just ignored her order or delayed it on purpose just so she feels that she did something wrong