Tweets from Emma during the Rio Games caused sideways glances - the Mirror said they included describing Laura as the "smaller uglier one of the family". She also joked about charging for interviews, saying later that she was "always happy" to talk about her famous sister.
Laura was born prematurely, suffered from asthma and a collapsed lung, and was pointed towards sport to help her breathing. She and boyfriend Jason Kenny are Rio's glamour couple, taking their combined gold medal haul over three Olympics to 10.
The Mirror said Emma's "lack of enthusiasm for her sister's win was immediately apparent to viewers, who shared their thoughts on Twitter." But Laura has tweeted that any suggestions of a sisterly spat are nonsense.
"If only you people knew. She is one of my biggest supporters She's been there for me through thick and thin. She was my idol growing up," Laura tweeted.
In the TV interview, Emma said: "Laura's not worked any harder than anybody else has.
"The amount of times that Laura kicked up a fuss on hills because dad and I were dropping her [and she said], 'if you don't slow down I'm going to ring mum, she can come and pick me up'.
"And I think back to them moments and I think how on earth was she the one that made it to be Olympic champion you know.
"It's incredible the amount that you go through, and the mental toughness, the stress, the anxiety, the can't have the Christmas dinners etc etc. Sport is the only thing you do 24 hours, seven days a week, everyone else gets weekends, that doesn't exist for a full time athlete."
Meanwhile, the Telegraph reports that it was hardly love at first sight when Laura Trott and Kenny met six years ago.
Laura said: "I didn't like him, I really didn't. If he was in a room with me he'd just sit there; he wouldn't come up to me."
