At about 3.20, she talks about hitting short balls. From what i can see, the person is feeding her pretty much no-spin balls and they're quite high, so they're easy to hit regardless. Against what sort of incoming spin is she suggesting this should be used? Is it against topspin, so you're basically playing a very fast chop-block?

I think she is saying:
1) when the ball bounces short, don't rush up and hit off the bounce, but wait for it to rise
2) if the ball is no-spin, the paddle should start above the ball (the high position, she said), and because the ball will be directed downward this is just a hit, mostly straight into the ball. One reason the blade is started high is because you're preparing for a bounce. There is some backspin as she hits it, but I think the emphasis is on the preparation. It's just a hit.
3) She said to aim at (just above) the net tape. (I will consider this, as my eyes are usually looking at the other end of the table.) Net tape is a convenient target. Never thought about it.
4) In my opinion the thing she said that was *most* important (to a shakehander), which I didn't understand at first, was this emphasis on holding the paddle upright (with the handle pointed down). The reason is, if this is your habitual motion, a small rotation of the wrist (imperceptible, or at the last instant) can send the ball left or right. (See for example Haruna Fukuoka, with the handle pointed down prominent in her game.)
5) She said that if the ball has backspin on it it is preferable to step around and use the (inverted) forehand, but that if you aren't fast enough it's ok to use the backhand (OX). Then she again suggested waiting for the ball to rise or reach it's peak.
6) Near the end she said that (a no-spin ball?) should be approached with the paddle in front of your body, but a floating ball should be struck by a blade coming from the side of your body. I don't understand that one.

Much of what I said above is based on what she said toward the end. She said: "Once the hitting point is configured in this way it will be difficult for the opponent to predict the course". (How can that be I thought? Because a small rotation of the wrist can send it left or right. That's why she's emphasizing holding the shakehand paddle upright like that. This emphasis on holding the paddle upright was the thing that caught my attention, and this must be the reason for it.)

At about 3.20, she talks about hitting short balls. From what i can see, the person is feeding her pretty much no-spin balls and they're quite high, so they're easy to hit regardless. Against what sort of incoming spin is she suggesting this should be used? Is it against topspin, so you're basically playing a very fast chop-block?

...
Another example of weird translation (not sure if it's in this exact video or another one of hers) - translator brings up 'building the wall', which in the end I interpreted as "lock the wrist" during the stroke. Hope I'm right - some input from a TT player fluent in Korean would be helpful here...