Stay and finish your education.
However don't be afraid to come here for a summer holiday
She can't since she's an illegal in America and once she leaves she won't be allowed back in.
I think you'd be crazy to leave America tbh. Not being able to travel back there to see your loved ones in the future would be absolutely heartbreaking.
Good luck making your decision, but at the very least finish your education.
And be aware that wages in Poland are miserable compared to America and your purchasing power will probably be about 25-30% of what you'd expect from a job in America.
re: jobs, so long as you speak good Polish you'll be able to find a job. The employment rate is pretty good now (the official numbers aren't great, but many, many people work off the books, I reckon the actual unemployment rate in Poland is more like 4%, officially it's 7.8% [Feb 2015]). The problem though is that the jobs market is very competitive and there's almost always someone willing to do the same job as you for lower money.
Poland's a great country with a lot going for it, but being completely honest I would not move here for work. Why do you think so many educated and/or manual workers leave Poland? The answer is money.
Why are hardly any of them returning?
The same answer. Money
Why work in Poland for pittance when you can have the same job in the UK, Ireland, Norway, Spain, France etc. etc. for 3 or 4 or 5 times the wage?