Glad to hear she finally confessed. Her reasoning seems a little... strange. Even from a girly prespective (and I've had my 'off my rocker' moments, I assure you). But hopefully she does press to resolve her issues. In the end, it's her who decides if she gets more stable or not.
And good on you for thinking about preventative measures with locking up your stuff. As terrible as it sounds, that's a really important step. Remove the temptation, so if she did consider something similar, it will require more thought than just 'impulse', and hopefully prevent any issues.