Tiff Watson joined Louise for a fitness session, with both girls displaying their super-toned tummies in cropped fitness tops.
And it's clear that the girls are closer than ever, as Louise called Tiff her 'sister' in a touching caption.
Louise said, "Me and the sister I never had wearing my gear, coming September."
Cute! Tiff is currently dating Louise's little bro Sam Thompson after the pair managed to overcome many a cheating drama.
Meanwhile Louise is looking pretty loved-up with her new boyfriend Ryan Libbey, who just so happens to be a personal trainer.
In fact, she's so happy with her body right now that she's launching her own activewear range, called Pocket Sport, this September!
Oh, and she shared this picture of herself in pretty peach undies.
While Louise was sharing underwear shots on Instagram on Thursday (11 August) Tiff was busy getting herself premiere ready.
She and her real life sister Lucy Watson turned up at the premiere for new Jonah Hill flick War Dogs in London. While Tiff opted for all-white Lucy went for a monochrome look.
Looking good, ladies!
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