You guys should leave. My mom doesn’t like when anybody’s in her room. It’s better not to get her upset. I won’t tell her you were here if you don’t.
Question: Do we need to put “IT” after like in the sentence? (My mom doesn’t like IT when anybody’s in her room.) Or we can leave it out?
In my (British) English, I would always include the ‘it’. This is either a American expression, or possibly an American colloquialism and you would still include the ‘it’ if you were speaking in a more formal manner.
Yes, unless you want to sound like Borat (a comedy character who spoke broken English).
To me they both sound natural. Including “it” is probably more correct though.
I could be wrong, but “it” in mom’s sentence functions as an “expletive” in the traditional sense of that grammatical novelty. (Not as a metaphor for vulgarity.) For example: “It’s raining.” What’s the “it” in this sentence? “It” is an expletive—a filler word to fill a void in a sentence without adding to the sense—extemporization. Mom’s aversion to anybody populating her room seems like a similar application of “it.”
You can definitely leave out “it,” and you should. It’s sentence clutter and only makes the reader’s task harder.