I will travel to Ireland next week with my sister. I have a study visa and she has a tourist visa. What kind of documents will the police ask for? I have already submitted travel insurance to the embassy for a visa. However our travel dates have changed, will they want to see new travel insurance at the border? Do they need bank statements, and is there a minimum amount of money in my account I should show?
It's very individual and really boils down to who's standing in front of you and how they perceive you.
They basically need to see you can support yourselves without resorting to (illegal) employment, and that your sister has incentive to return at the end of her stated duration of stay.
So your sister should bring bank statements along with a return ticket.