Sure they do, but it’s not the main component. Wither scratching for the right answer is R+. for example.
Liberty work + immediate R+ kind of doesn’t work, unless the horse loves verbal rewards, or you’re working no more than arm’s length from the horse’s withers or head or whatever his favorite itchy spot is. Most of R+ is an active thing - touch, treats. And if a horse isn’t all that verbal-centric, it can take a bit of time to associate treat/touch rewards to the voice as a reward
What is your friend’s definition of R+? IME, way too many people don’t understand R+ vs R-.
Liberty work really comes once you can do on-line work without using the line much or at all. Is she to that point?
If someone is working at liberty because a horse isn’t safe to be attached to yet (lead/lunge line and halter), then the work is actually R-, not R+. If you’re watching the horse as he’s trying to get away from you and then in an instant he stops and looks at you, you immediately look away, which is R-, as you’ve taken away the negative aspect which is your looking at him.