She starts by accepting this arbitrary rule that someone hallucinated, then writes a sentence like:
Joe opened the door and walked out into the hall.
She then says that sentence is wrong because Joe didn't open and walk at the same time.
Well I'm here to say that "and" doesn't always mean simultaneity. In plain American English, as it is used by humans, "and" can mean sequence just as well as it can mean simultaneous action.
When I say, "I ate dinner and dessert", do I have to mean that every bite of dinner was mixed with a bite of dessert? Not on my planet.
When I say, "I drove to the store and bought a gallon of milk", do I have to mean that the milk was bought during the drive? Obviously not.
Changing that conjunction from "and" to "and then" may be more specific, but it results in an extra word.
On the one hand, if you have "then", which is called a "conjunctive adverb" when performing that function, you don't need "and" - "and" is completely optional. (If present the word "and" demotes the word "then" to a plain adverb.) On the other hand, unless the reader has a reason to believe that Joe can walk through closed doors, then the sequence obviously follows from the order of the sentence, and "then" is unneeded.
Purists, like Uncle Jim over at Absolute Write, say that "and then" is never correct, because at least one word is excess. This comes from the journalism school of writing, where every word must be savagely assassinated if possible because you have to pay for telegrams by the character. Did I mention it's an old rule? Then Uncle Jim unfortunately perpetrates the same "the word 'and' means only what I say it means" line of manure.
I say, all three constructions obviously mean the same thing in English. Use whichever one sounds the best in context of your story.
Final statement: the rule is only necessary where (1) there might be confusion about whether the actions in the sentence happen at the same time, and where (2) that confusion matters to the story or the reader. If those two are both the case, you can save two words by using a punctuations mark: a period.
(Use semicolon only if you are an expert.)