rent responsibly from a known quantity
Not a realistic possibility in Poland.
why does she demand half of the rent in cash
have decided to end the contract aswell before the 1 year contract is over. Will i get my deposit back
That's the right decision considering she's entering your home without asking, using landlord's keys. They never pay deposits back though unless they are forced to. Unfortunately Poland doesn't have a system like the UK where the deposit has to be paid into a government run fund who then decide if the landlord's claim on it (must be backed up with photos or other hard proof of damage) is valid.