What? Why would he choice that time to tell her that? That’s just so unnecessarily dramatic and ridiculous, he couldn’t wait until they got home?
It may not be that was when he told her... she may have known... he might have just said something bland like "Thank you for being my partner; I wish you well."
Whatever it was, it was a very emotional moment for her. It's worth noting that in a practice session at that comp, she fell in a lift and spent a night in the hospital with concussion symptoms. So, really it might have just been the whole conflagration of events taking their toll. Still, it is heartbreaking to view the footage, which I cannot find now.
I guess what surprised me most about this episode when I learned about it in later life... was that the Soviets actually let them split. My notions at the time (and to a certain extent, now) were that the authoritarian State would have decided that it was in the collective interest for them to remain a pair.