The X Factor winner, 17, braved the winter temperatures in a Calvin Klein bra top which showed off her taut tum and enviable physique.
Louisa was all smiles as she posed for a picture with Jack Pack, fellow guests on Graham Norton's radio slot.
She is currently promoting her new single 'Forever Young' after winning the ITV singing competition last weekend.
She came first, beating Reggie N Bollie to the top spot.
Simon Cowell hailed her as "the best ever" act he's ever seen on the show.
On Friday night (18 December), Louisa appeared on ITV1's Text Santa where she even helped take donation calls.
The three-hour show included sketches from Downton Abbey and Coronation Street, as well as a live performance from Louisa.
It's been a whirlwind week for the pretty singer after her amazing win, but she's also been hit by negative press after her single entered the UK charts at number nine.
The Telegraph describes it as: "The worst performance from a winner's single in the show's 11-year history [...]. She has achieved combined sales of just 39,000 with the single."
We think Top Ten is pretty amazing for a singer who nobody had heard of three months ago, though!
Louisa Johnson (@louisa) December 13, 2015
Louisa, however, is keeping upbeat and told her 232,000 Twitter fans: "Cannot WAIT for next year..."
Lots of fans responded with supportive message, with one saying: "Cannot wait for your album."
Another replied: "Can't wait to see what music you have for all us fans."
In 2016, Louisa will turn 18 and take part in the X Factor UK tour, which kicks off in February.
To find out more about what Louisa's been up to since she won The X Factor, watch her Winner's Story on Sunday 20 December at 6.25pm on ITV2.
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