It sounds like Aldora was given conflicting directives - assign me to the DM who is handling inexperienced divers looking for easy dives but also assign me to the boat with experienced divers looking for challenging dives.
That is unfair …
I think her DM, who knew what her diving requirements were since they had been made clear to him, had a duty to explicitly let her know that he was being assigned to guide inexperienced divers and to explicitly give her the option to switch to a more experienced group.
As a staff member he has access to the dive roster and it would be covered in the staff briefing.
As a customer the OP would not be aware of the behind the scenes roster allocation of divers to DMs.