Well, it's not what I would do, but I feel like as long as she's honest about the conditions of the party, people can decide whether they want to come or not. So at some point when the invitations go out, she should be letting people know it's BYOB, potluck, paid parking. Are there bathrooms nearby? Does the shed at the beach have furniture? It doesn't sound like a party I would attend, either, but again, if everyone knows the score before RSVPing, at least they're making an informed decision.