"Why not? It's not like they're going to care if it's you. Richard always cooks like enough for an army anyway." Beverly is going to keep on this until you agree, Simon because that's the way of her, and she recognizes a lost kid when she sees one and Simon is a lost kid despite the age difference between them and what she knows about him. "What's the worst that could happen?" It's not hyperbole, a rhetorical question that she casts at him. Instead, it's a real question that she honestly just wants the answer to, about what he thinks about this.