Dog doesn’t seem to mind being humped, should I still stop other dogs from doing it?

My dog is a spayed golden retriever, and she’s very patient with other dogs, babies, and so on. I’m dog-sitting a male lab (no idea if he’s intact or not) and he’s… very humpy with her. No actual futile attempts at procreation, just humping. Literally every thirty seconds or so. As far as I can tell she doesn’t seem to care much — she occasionally pushes him off, and when it’s happening she sometimes looks at me, but I can’t tell if it’s for any reason other than that she always has her eye on me. Her expression stays pretty neutral.

I’ve so far intervened every time I’ve seen it, but it would be nice if I could leave them to play together without worrying I’m traumatizing her. I also feel bad correcting the dog I’m sitting so much more than mine, like I’m playing favorites. Should I keep intervening? If so, any advice on what to do other than just verbally correcting him when he hops up there? Any insight is appreciated.

Edit: thanks for the comments, I’ll keep correcting. I want to do what’s best for both dogs.