Thanks for the replies everyone
Well it looks like it didn't happen. We tried holding her for him, he'd mount her, start thrusting but they never tied. He'd just stop after a min or she'd start moving around and he'd fall off. They were together outside for awhile but I doubt they tied. And now he's seeming not interested in her.
All is well though, AI was never an option as breeding wasn't that important to us. If it didn't happen - it didn't happen, no big deal.
Since she wasn't receptive towards him (and wasn't her last heat either) is it safe to say she'll never be bred? I'd love a pup from them, but if there's not much chance she'll ever be receptive, I might as well just get her spayed.