That depends on where you are. If you are in a state that allows recreational cannabis use, as long as your friend is old enough to purchase cannabis (and they have your Leafly Pickup number) they can.
At a medical dispensary, only you or a certified caregiver (if applicable) can pick up your items. Please check local laws before sending a friend to the dispensary in your place. When in doubt, you can always text the dispensary after you send in your pickup request to confirm.