Yes she made the choice to buy alcohol, but the provider supplied it to her at their location. If she got drunk at home, went to the venue, was kicked out and crashed then thatd all be on her. But the venue provider her alcohol, enough for her to become intoxicated thus changing her from a person capable of making her own decisions reasonably to a person unable to reasonably make her own decisions (with regards to her safety and the safety of those around her). The moment that switch occurs her safety and those around her are the responsibility of the provider and removing her from the venue/location requires a safe/reasonable means of transportation. Its the same reason you cant just drop a drunk person off on the highway. Its unsafe for them and those around them. Its also the same line of logic for why an intoxicated person cant consent. They are unable to make soind decisions regarding their own safety. So, you cant kick someone out of location after getting them drunk only to have them drive a vehicle.

Its one of the bigger reason why bars take peoples keys when they order a drink.