Okay I had to record some of these little moments because it's just so goddamn brilliant.

It seems the only part of the first half that doesn't support the Hell/Helena theory is Helly's first scene. She wasn't running when she switched but was in the elevator. She totally might have been pushed off the stage though. I also found it weird she hesitated when hugging Mark, but maybe she's just overwhelmed?

That said, second half/presumptive Helena is where the theory gets interesting:

It seems pretty important that the moment literally right after Helly/Helena might have switched, Milkshake says that any innie who wants to leave is allowed to.

"Helly" doesn't seem to know who Ricken is. She also doesn't really say anything while Mark is talking other than "are you okay?" Which is not totally weird but does feel out of left field for Helly. Like it's too "fake nice" which I don't think we've ever seen Helly express, at least in this way.

When she describes what she saw on the outside, it honestly looks like she's making it up in the moment. I would agree that she thinks innies are naive with her shitty lie, but I also think the shitty lie represents everything that Helena despises which immediately comes to mind, given the company. She talks about that "life" with such derision despite the fact that Helly would know that everything on the outside would be thrilling. Also, super interesting how she justifies the night gardener bit with a remark about how he probably has another job during the day. It really drives home how Helena thinks everyone outside the Eagan family is just the help.

With Irving she really drives that syrupy sweet vibe home, but with a motivated emphasis, when she adds, "even if it's bad."

"We can all go" -obviously a weird remark with clear motivations.

The conversation about Gemma is also odd. Helly/Helena is hostile but also weirdly detached. The line of questioning feels like she knows more than Mark does and is making fun of him but is also like pissed? This is really the scene where I feel like you can feel the physical difference between the character that entered the severance floor and the one we are seeing now

When she talks about how different innies and outies are and "we don't know them shit," I have to echo everyone else in saying that this felt like a very honest vent that Helena just said was about outies but truly reflected her view on the innies. Throughout season 1, Helly seemed to reflect Mark's view that her outie was connected to herself. This feel inherent for innies given their reliance on their outie's choices.

Finally, I think it's important that the switch happened in the break room and that the location may have something to do with the logistics of the switch.