For a job, can I teach the English language? She is already looking for a flat. Should I be worried?
Yes. Legally working in Poland is easy if you're EU, but if you're non-EU, there's a fair amount of regulations that you'll have to go through. You'll have to get a job lined up before you come, you'll need a work permit in most cases and you'll need to get the relevant visa.
Whatever you do, do not come to Poland on a tourist stamp and overstay.