Upvote:8
As a practical matter, your daughter, if she travels to the US for a month, earns no money, and flies home (or at least out of the US) afterwards is not likely to run into any trouble if she travels under the Visa Waiver Program.
One of the activities which is explicitly allowed under a tourist visa or the visa waiver program is:
enrollment in a short recreational course of study, not for credit toward a degree (for example, a two-day cooking class while on vacation)
which seems to match very closely with your daughter's proposed activities.
If there is any doubt, it might be wise to contact the school where your daughter will be studying to seek their advice.