I think the answer to the original point of the topic has been given:
Charm seems to not work.
Additionally: If something says it's resisted by magic armour, then it'll only work if the target has no magic armour. But most people already know that and it's pretty much a given that when we're talking about applying effects, we're implying that armour is no longer in the way.
Lastly, as a general rule, we're supposed to test the game while it's in alhpa/beta. This means everything from playing as intended to looking for edge cases that break the game. And everything in between.
The reason I raised magic armor issue is to try to narrow down whether there was a bug (charm arrow not working when it was supposed to) or a feature that went unnoticed (charm blocked by magic armor or a characters immunity to the effect). Because magic armor is new do DOS2, some people may not be up to speed on its gameplay mechanics, or forget about it. I know I did during some fights in my first play through.
Charm arrows worked in my game, though I did not try them against Emmie so I can not address that specific use. Just trying to get all the details so the Larian folks can determine what (if anything) caused the bug, or how to make the reasons for charm failing (where intentional in the game) clearer.