Sometimes no answer is the loudest one. Cloaking the ship and turning away was an emphatic exclamation point at the end of it. Natasha understood immediately; she wasn't the 'Widow' for nothing. She'd loved and lost so many times before, but she'd hoped this time would be different… Bruce was different; she was different with him.
She'd pushed too far, too quickly, and this was his answer - loud and clear. It wasn't in her nature to be with someone. Widow wasn't just a honorary title; it was her very identity and her only destiny.