You don't? People will do horrible shit to one another intentionally and unintentionally. If you hold the unintentional against them, goodness knows why they should have any motivation to do otherwise. At least they're more likely to do it differently in future.
It happened to her whether you saw it or you didn't, whether you're well intentioned or not, darling. But you saw it. You can make the best of that or you can do sweet fanny all with it. It's no skin off my nose.