A It’s dicey to try to give this kind of feedback. A peer may not take kindly to unsolicited criticism.
The best way to alert this coworker of her “laughing problem” is to broach the topic with her boss. Say, “She’s great in many ways, but in this one area she may not realize she’s a distraction and it affects our productivity.” Ask the boss to keep your identity in confidence and suggest giving this feedback as part of her normal , as long as it’s not months away.
Just make sure not to isolate your complaint as the only thing you say to her boss. Throw in the things she does best to show you’re being fair. Mention any steps you’ve already taken and the results.