@Isthisexpected : that is absolutely bloody awful for your friend, so sorry
defo complain to AirBNB with screen shots (which does not help you tonight)
Re actually getting in: I have one ‘last resort’ suggestion for those traveling with a person needing access & a time restriction.
This is: leave the person requiring the accessible route somewhere comfortable, but close to Westminster/Tate and queue yourself & get a wristband. Get through to Victoria Gardens & speak to Marshals there - this is a spot where people who joined the ‘regular’ queue but SHOULD have been in the access queue get ‘diverted’ by the marshals (saving about 3 more hours of standing). No guarantees but as a last resort this is what I would try and might allow the person you are traveling with to get access when the access queue is ‘closed’: I appreciate this would only work if there are enough of you to split up / the less mobile person is comfortable being left alone but if it helps anyone this might be an option