Yuck. Sounds like she's having trouble adjusting to both a new family and hormones all at once. I often lose patience with my sister in law who after 4 years still tries to keep my brother and the kids distanced from his side of the family. Be as patient as you can.
No, no, no, you're doing it wrong. You're not supposed to answer MUD seriously. You're supposed to give her bad advice on purpose, or post a picture of actual mud, or make fun of her spelling and grammar. Don't play into it!
Here's my contribution: