Does shortening and butter go side by side for measuring? Want to make cookies but my grandma can't have butter

Ok thank you!! :) true puffy cookies are good lol

She can't have milk, it bothers her

Sort of. Shortening is 100% fat and butter is about ~80-85% fat. You would need to use less shortening and add a little water. If you do a 1:1 substitution for a cookie recipe, your cookies might be puffier and softer. Which isn't exactly a bad thing. It really depends on the recipe and the type of cookie.

Why can't she have butter? (If it's because of the fat content, she won't be able to have shortening either.)