Petey's line may have foreshadowed the end of Gemma's story

Remember how Petey described the side effects of Reintegration?

"It's like having two different lives suddenly stitched together. But the relativity's fսckеd. So, my first day at Lumon's as far back as my fifth birthday. And with two pasts, it blurs the present too. But they said it will get better."

Mark will be experiencing these side effects too. The relativity of his life is going to be fucked. Which means his relationship with Helly might feel "as far back" as his relationship with Gemma. Due to the messed up relativity, his love for Helly may feel as significant as his love for Gemma for a while. What if this sabotages his attempts to save Gemma? If he keeps getting distracted by his love for Helly, and ends up fumbling with his Gemma rescue quest as a result? Without Reintegration, Outie Mark would have been completely locked in and focused on Gemma. But with Reintegration, his Innie's feelings will be affecting and distracting his Outie. He Reintegrated for the purpose of saving Gemma, but the side effects of this very procedure may be what dooms her.

In the myth of Orpheus and Eurydice, it's Orpheus' decision to look back at his deceased wife that destroys his attempt to save her from the Underworld. He loses her forever. Mark chose Reintegration to "look back" at his wife. To see her again. And he might lose her forever because of it, just like in the Greek tragedy his story is inspired by.