This is an interesting sequence of events. It appears that this man sent his girlfriend a message, asking her if she wants to "lock feet" with him (if that is even a term). The girlfriend thought what any sane person would - "No way, just get the hell away from me!" In reality, she was slightly more understanding. She wrote back to him, saying that she can't verbalize how much she doesn't want to lock feet with him.
We don't know what happened next, but hopefully, they didn't break up after this. It all depends on whether the guy was serious or ironic sending this message to her - after all, perhaps this was some kind of inside joke the two of them had? Otherwise, why would anyone request this from their girlfriend, instead of the myriad other semi-sexual options?