It looks like the others have already given you some good pointers on what to look for. The main thing is these two jerseys are the current ones. She'll probably want one of those two. The primarily green one is the home jersey, primarily white is away. You might want to try to get a feel for whether she'd prefer the home (green) or away (white), but I'm going to take a guess and say that the green jersey is your best bet. It showcases the team colors more strongly than the white jersey.

When you make your choice, it wouldn't hurt to post another link on here and ask if you chose the right one just to be safe. This might be what you want, but I don't know for sure if this is an authentic or replica jersey, don't know if there's a better place to buy a jersey, etc. I think the others can help you with those details better than I can.