Sorry, picked upon this far too late as usual. Zero hours contracts, graveyard of the soul and the best opportunity for unscrupulous or bad managers to bully their staff with threat of no work. Our daughter was on them for a couple of years after uni, our son's been on one for about 4 months. Mostly skewed to employer's advantage.
You're better off out and your manager clearly knew she was in the wrong when you called her bluff, sounds a nasty piece of work all round. For future reference, as a rule of thumb, the guidance on notice was always monthly paid, one month's notice, weekly paid, one week's notice, unless your contract specifies differently. That's probably been turned on its head now.
Walk away, kick the dust from your shoes and don't look back. Good luck with whatever venture you next undertake.
Regards,
Chris