The couple met while they were shooting the Twilight series and are famously private about their relationship, refusing to confirm it for years.
This summer, Kristen admitted being unfaithful with married film director Rupert Sanders after pictures of them canoodling were released. She is thought to have briefly split from Robert, although they have apparently since reunited.
The pair are teaming up to promote the last vampire movie Breaking Dawn - Part 2, with Kristen quizzed about whether she and Robert are back on track today.
"Funny you mention that," she stammered on the Today show. "I'm going to just let people watch whatever little movie they think our lives are and keep them guessing I always say."
Although Kristen appeared embarrassed by the personal question, she smiled as she was answering. With her head bent low she appeared bashful but happy, leading many to take it as confirmation the romance is firmly back on.
Earlier this week, Kristen's friend Dakota Fanning slammed people for their interest in Kristen's romance. She insists the two stars should be given the space they need to repair their relationship.
"Everyone thinks they have the right to, you know, publicise the struggles and sadness and heartbreak and all of that," she said. "It’s like, ‘Why do you think you are the authority to judge people’s experiences?’ I can't talk about it."