Thank you so much for your time,
Here's what you can't do: tell her she 'laughs wrong'. I'm sorry you don't care to hear her laugh, but people laugh how they laugh, hyena, donkey or howler monkey.
I would try an entirely different tactic. Love her, warts and all. The poor thing seems to have no friends. Her off putting laugh, her gum chomping and overbearing style of conversation has made her a social pariah, which is a never ending spiral of loneliness and misunderstanding. Perhaps if there was someone who could be a little more tolerant, just a little more tolerant, that person would have her ear and then that person could say things like, "Oh, darling, watch out with your knees there! We can see all the way to the Jupiter..." or "Excuse me, I wasn't finished making my point. If you would just let me finish." A friend can tell her, "I don't care much to talk to you when you talk over me."
I do grow weary of the the phrase, "What would Jesus do?" but He did have some difficult people around him. Today is the feast day of St. Mark, the Evangelist. St. Mark had traveled with St. Paul and after that St. Paul specifically requested that St. Mark not travel with him on the next trip. Perhaps St. Mark was a gum chewing over talker. Maybe he snored.
But in the end, St. Paul asked Mark to visit him in prison. We'll never know if Paul asked Mark to take that gum out of his mouth.
Also, make another list. The list of things she does well. The list of things that are lovable about her.
I can tell you this: it takes a brave person to befriend the social pariah. Because a person who befriends a social pariah runs the risk of becoming a social pariah themselves.
Jesus was a bit of a social pariah, precisely for this reason. I guess we now know what He would do.