Margaritas

If, at a group dinner at a tasty Mexican restaurant, where all parties were having a couple drinks but not getting drunk, one person took it upon herself to order a half-pitcher of margaritas with no intention of sharing, would it be inappropriate? If she proceeded to drink the entire half-pitcher, and then pour a drink from a neighboring pitcher, would it be inappropriate? What if she were to be the only person really drunk at this event?

Could any innapropriate-ness be dispelled with the fact that a regular margarita cost $4.55, and she was sure to want more than one, the jumbo margarita, usually a good choice, cost $7.10, and the half-pitcher was on special for $7.75, making the half-pitcher clearly the best deal?

As for the extra drink poured from the neighboring pitcher, well, I guess I'm just an alcoholic.