The question basically says it all. It's that woman who is working for a gourmet. She buys items from you. I know she'll buy Berry Juice and Tiny/Big Mushrooms, but what else does she buy? You don't have to list how much she buys them for.
She will buy any berries and mushrooms from you and these items: Sweet heart Stick Fresh water Leftovers Lucky egg Soda pop Lemonade Honey Moomoo Milk Berry Juice Castelia Cone Lava Cookie Old gateau RageCandyBar Shoal Salt and Rare Candy.
Source: http://bulbapedia.bulbagarden.net/wiki/Item_maniac
Hope I helped!
