lol, seriously, what are you talking about?
You cannot be serious with this nonsense. You can leave her behind a couple of times but then she will be driven mad by voices in her head to attack your party...if you then say you let her stay the voices instantly stop and she collapses on the floor unconscious, asleep. If you refuse she will attack and force you to kill her. That is by design and again by the rules of the DM. Please go back and read the bloody thread.
Which would be... Her. Initiating. The. Combat.
See?
It's not... Rag. Initiating. The. Combat.
It's her.
I've read the thread. In fact, the only reason I'm replying is because you keep repeating yourself.
Why are you repeating yourself for no reason? You literally have ZERO points. The game makes it abundantly clear that your ONLY choice it accept her in your party or kill her. End. Of. Story. There's nothing more to it, yet you keep repeating nonsense over and over and over because you refuse to accept that which is literally the EXACT same thing as refusing to accept DM ruling. So as I said before: your only option is accept the DM ruling or leave the table.
If I'm reading this whole conversation correctly, the issue is that the game offers you the option to make Shadowheart leave, she agrees to do so but then proceeds to remain in your camp anyway. Her being sworn to guard the artefact has nothing to do with that. It's clearly either a bug, an oversight or an Early Access thing, @JandK and others are completely in the right here.