She should consider applying in Ireland. Ireland's divorce laws and legal system are far more straightforward and inexpensive. Also her husband is less likely to contest the divorce if it's going to go through the Irish courts as he will feel less confident than he would on his home turf in Poland.
With the situation you describe, they will grant the divorce anyway even if he contests it. The only stumbling block is the five year thing, that is, you need to be living apart for a total of four years out of the previous five. If her husband can demonstrate that they were living together and that he objects on those grounds, she can simply say that they were living under the same roof but the marriage had ended and that she stayed there because she couldn't afford to move out. Q. How do I prove that I am Separated for four years ?
You will be required to complete a document called the "Family Law Civil Bill" in which you will be required to state the date you were married and the length of time you and your spouse have been living apart. You will be asked under Oath in Court to verify this information.
So basically if she's prepared to lie about it........however, the court could ask to see evidence that there were two separate households within the same house, ie separate bills but most couples don't go that far so there's a good chance that the court will accept her word. It's worth a try anyway. They have no interest in trying to force unhappy couples (especially when they're not even Irish!) to stay together where there are no children involved. She's been living with another man for two years so there is clearly very little prospect of reconcilliation.
She doesn't even need a solicitor for an Irish divorce. With no kids or property involved, it's very simple, a few forms to fill and get notarised, won't cost her more than a couple of hundred euros. All the forms are here: