I'm not entirely sure what "teach her to chew" means, but given that she was 5, she had to be eating somehow by then, and chewing is a mechanical variation on the sucking motion, so I suspect it means "chew with her mouth closed". And 5's a bit young to my thinking. Even typical kids don't really have much of a "theory of mind" at that age, but since they're wired to attend to social performance, they're more likely to mimic socially appropriate performative behavior. Chewing with one's mouth closed is Performative behavior. If that seems anything other than obvious (at least once it's pointed out) then see that as an indication that you're wired on the social performance end of the typical-divergent spectrum. Probably, she'd have learned more naturally around age 8, when the normal developmental shift into the tween years increases a child's awareness of "the other" - although it's entirely possible someone would still have needed to say something like "you know, other people don't like to see mouth goop - you know how you don't like goop on your hands? it's that kind of thing." A 5yo won't understand that - even a nt 5yo! What a typical 5yo will get is "this is how to perform eating".
We had to teach her how to speak by rote memorization of responses to certain phrases and then build off of that (at 5 years old)
If you take "teach" out of the equation, what does this look like? It actually looks like a pretty common experience for divergent kids, which is that they pick up on whole phrases and "scripts" and learn those first - much the way, if you were moving to a place where people spoke a different language, you'd learn common phrases and responses first. "How do you do?" and "Excuse me, where is the toilet?" In a way, it's a more "adult" learning style - but it's only possible because the person in question has already internalized a lot of the rules and patterns of language. It's not at all like teaching a parrot to talk.
But it's not so much Different from the way neurotypical children learn as it is more overt. One of the current fields of study is how much normal, day-to-day human behavior is scripted or even "robotic" - people run on autopilot. Neurodivergent people are more aware of the scripts and subroutines. I certainly am - even before these ideas were in common parlance I thought of myself as having a set of internal characters I could move to "center stage" and have them run their lines for my "audience". It's interesting to note that a lot of performers are neurodivergent - makes good sense, if you think about it: they're more aware of the extent to which daily interactions are performative.
Blank face, no words, nothing.
It's called "resting face". And it throws neurotypicals into an amazing amount of confusion and distress - it's really a fantastic window on the gaps in their wiring system because Everyone has a "resting face", but when a person expects a socially performative face and sees a resting face, they have a negative emotional response. So we have the expression "resting bitch face" to describe women who wear their resting face in public. And when people default to a resting face while... watching tv in particular, it's said they look like a zombie. Producing resting face when other people expect emotional performance is called "flat affect" and considered a symptom of a number of disorders... many of which, it turns out, may be neurodivergent responses to... well, to being bullied to "act right" our whole lives.
A whole lot of parent-child miscommunication ends up being about resting face or failure to perform the "right" other face. This is something a lot of divergent folks are distinctly aware of - hands up anyone who's ever thought "do I have the right face on?" You're aware of the space between your internal state and outward performance. And while neurodivergent folks tend to be more intrinsically aware of that space, it's certainly something nts can learn - it's a big component to things like meditation, mindfulness practice, physical disciplines like yoga and tai chi, and even acting!
As a parent, any time you find yourself upset that your child isn't showing respect, or courtesy, or appreciation, or attention, it can be helpful to pause and remember that all these things are Performative. And that sometimes it's harder to perform than others.
And I can't emphasize enough that, even though I'm drawing a line between neurodivergence and typicality, this is stuff that can apply to any kid and any parent - even to adult-adult relationships. Conventional parenting/education is all about demanding a certain kind of performance from children - a performance that's as much about power dynamics as anything else. People in power get to have resting face. Lower status people are expected to put on a pleasant expression, to show that they're listening, to appear interested and attentive. So this stuff crosses a lot of lines into various 'isms - sexism and racism and classism - but we start learning it as children. Age 2 is around when adults start reacting to a failure to perform on the part of children. It's part of the "terrible twos" - kids "demanding" things instead of "asking nicely" is a common performance fail, along with kids saying "no" rather than cheerfully acquiescing. Kids who don't start to work out the performance details quickly get categorized as "bad" or "difficult" or in need of teaching. All kids benefit from adults looking past their performance failures and seeing little people struggling to deal with a complex and often overwhelmingly big world.