This quote obviously refers to the violence by which she dies, which heavily impacts her experience in the afterlife. It also suggests that her injuries, prior to Mr. Harvey killing her with the knife, are serious enough to kill her.

The making of the trap, the luring Susie into it – these are not mere preludes to violence. But links in the chain of violence which culminates in her death.

This act, forbidding Susie to leave, is overtly violent. He is no longer pretending to be nice. His words express the depth of the brutality that will swiftly come.

Although this is not the most violent thing Harvey does (if we can weight these things against each other) it's extremely impactful. Seeing him shut off her breath and voice gives the reader a vivid sense of suffocation.

Instead of the violence itself, we are seeing its impact on Susie in the moment. Her inner life has been, in a matter of moments, utterly transformed.

Susie has no illusions of continued life at this point. But, this sense of renewed life, of a moment of relief, is a powerful observation.

That kiss with Ray was the extent of Susie's sexual experience before Mr. Harvey.

At the end, we learn that Susie is telling her story from wide wide Heaven. So, it seems the hole is forever stamped in her memory. Now that she knows eternal time, the hole is both eternally far and eternally near her in time.