I tried to keep one last year and failed dismally. They're often quoted as being hardy, but I am full of disbelief, I'm afraid, especially if we get a long cold spell. Good luck with yours, though!

I know i have my micro climate here but ....... Nemesia 'Confetti' is described as hardy and has come through the past 2 cold winters without a hitch.

I don't know how cold Essex gets but over 'here' these plants are described by 'me' as tough as old boots.

Analyse your specific area ..... your home location, plants position/orientation, the soil and drainage ..... and so on.

It's bizarre that Spritz lives in the same county as me but more westwards and hers didn't succeed ..... i'll harp on again about individual sites and positions :-/
Just depends on where you're expecting it to grow.

I have a soft pink one that has been fully hardy even in a pot over last winter. I always take cuttings just in case I lose the original plant.