Ice aren't bad and are a good value for the money. They even offer sets of three: 3-stop, 6-stop, and 10-stop all for one filter size. Just be sure your friend buys the largest size diameter. She can always use a step-up ring which will allow any ND filter to be used on smaller diameter lenses. It's much cheaper to do that than it is to buy separate ND filters for every size lens. Typically 77mm or 82mm are the most common, but if her largest lens is 67mm in diameter, then that might be the best option coupled with step-up rings (which aren't expensive).