I agree that the N/S bidding was bad (at least South's bidding, 2♥ seems reasonable to me), but the number of tricks taken and the results from the other tables leaves the impression that the general level may not be very high. The initial double would not be my choice, but when that was chosen it does seem like it was misinformation that created South's final problem. I believe her when we are told she would have bid 3♦ if 1♦ had been correctly alerted and explained. An experienced/strong player may have found that something was wrong if East had shown 12+, West 6(?)+ and North 9-11(?) when she herself got 15, but this player didn't. While we can dislike the pass, she now got a bidding problem with no obvious solution. The link between subsequent and consequent doesn't IMO depend on how big an error that is made, but if the error is directly linked to the infraction, and that seems to be the case here. Also, if you consider this a "very serios error unrelated to the infraction" (§12C1e) then you shold normally award a split (non-balancing) score.