The idea of “the DM is always right” is a lot like “the customer is always right”. It’s only true when nobody needs to say it.

Bruh imagine being so bad at DMing that you ruin the game for your girlfriend.

The punch caught me off guard. Even if the DM was remorseful, he showed that he never deserved a friend like OP.

“She’s your sister”
“I dont have a sister”
“You have amnesia”
“no i dont” Then proceeds to stab her

Because of course, playing your character, and killing a DMPC justifies real life assault-

This is not your standard everyday pissed...
This is advanced pissed.

OP: Do I succeed?

DM, standing up: Correct. Now roll initiative.

Let me tell you something: My boyfriend is a DM, and I play in one of his campaigns. He occasionally reveals bits of plot and story to me, or alludes that something in the game is not what it seems. Even though I get a tiny bit of an upper hand since I know a few things the other players don't, I refuse to use that information AT ALL. My boyfriend knows this which is why he trusts me with game information. I also know that he will not hesitate to kill my character if I do something unbelievably stupid, aka no plot armor for me.
Now as for the girlfriend, if she can't keep her damn mouth shut and treats out of character knowledge like a bunch of cheat codes, then she should NOT have been given special treatment. And by the love of the gods her being part DM was perhaps the worst choice her boyfriend could have made

Now, I have an unpopular opinion here: DMPCs aren't, by default, a bad idea.  They can be a great way to fill a gap in a party dynamic or a last ditch rescue if every single person beefs their perception checks on a puzzle or something.  BUT.  Just like any other idea in D&D, it has to be done carefully.  You can make an NPC or DMPC a participant without making them the hero of the story.  Step back and let the players speak first.  Roll everything like you would make your players roll.  Use the DMPC as backup, not as a star. (one of our NPC party members was kind enough to do all the looting for us while the PCs were having a major in-character argument, which I appreciated.  Let us roleplay while also making sure we didn't miss out cause literally none of us thought of it at the time lol)

The moment the girl brought up the paladin plot twist, I'd have one foot out the door. The moment everyone else dismissed it, I'd be gone. No, saying a plot twist will happen but "you won't know what it is anyways so what's the difference?" isn't a thing. As soon as you mention a plot twist regarding a character, especially "you better watch out for him!" that ruins all other possible routes for a character. Instead of being complex, dynamic, torn, or whatever, they're now a walking plot twist.

Any person who punches their "friend" over a slight in D&D (or any TTRPG for that matter) is not a person one should be friends with. Good on OP for dropping him & even better for not stooping to his level. Though in all honesty I would have laid him out for that but I'm not a better man...

This is my girlfriend 🚩
We're co-dming 🚩
She has no experience with ttrpg 🚩
Has DMPC 🚩

DMs: stop inventing relatives that the players didn’t tell you about.

Seriously, this should have been a "I'm outta here!" after the first session. Yet another fine example of "Better no D&D than bad D&D".

If GM's GF was smarter, more imaginative or simply more experienced she could have played her character as a minion to the BBEG or conversely an emissary of the light. Hindering the party's progress or covertly guiding their actions. Not openly metagaming but acting as an Oracle or Seer.

“The  GM is always right “ I would have punched him in that moment ngl
EDIT AFTER FINISHING THE VIDEO: THE GM HIT HIM?!
It’s so funny that he was so pressed about his gf character’s being dead and getting a nat20 that he punched a player AND THEN TRIED TO APOLOGISE
I imagine that his apology is the kind of “sorry but you made my do it”

So a surprise attack DOES work, even though he's right in front of you.

Reading the title i thought the GM would ruin the game by making his GF uncomfortable andruin their relation... On one hand i am relieved no girl had to suffer from it this time, on the other, i don't know how to feel about the girlfriend taking a clear joy being GM's pet to do and say whatever can ruin the mood.

The girlfriend's the type of person to spoil Snape kills Dumbledore then writes self-insert canon-rewrite fanfics.

As much of a spoiled brat as she is, I hope the DM''s GF sees how badly DM reacts to mild slights and breaks up with him, safely with a friend nearby. That's a guy that punches holes in walls and brags about it. That's a guy that will beat you.