The 20-year-old said she used to dish out boyfriend tips to her pals.
She told US Allure magazine: 'The best way to get a guy to like you would be to actively ignore him, I was filled with advice!
'I'd tell my friends things like, 'Don't accept that apology, that isn't sincere!' Or, 'he hung out with his ex-girlfriend? Get rid of him'.'
But these days the Mine singer, who is rumoured to be dating Jake Gyllenhaal, has realised love is not that easy.
The star added: 'But love is never that simple, now I'm finally getting the idea it's the one thing I don't need to have a strategy for.
'I can only write the material I know, which is what happens to me.'