Obviously, for this type of letter, you want to adhere to the instructions and the tone, so feel free also to use phrasal verbs and colloquialisms, any slang.
What we do know is that YouKris posted the photo in early August 2024, and according to Chinese media, many of the comments are local colloquialisms that don't translate well.
Eating for two is a nice colloquialism, or it's a nice little saying, saying that person's bigger or they're eating a lot of food because they're pregnant.