ozflier, some other points for consideration:

1. How tall is your daughter (i.e. what are her legroom requirements). For some with lesser legroom (i.e. QF, CX, BA) it might make a difference)
2. Who's paying for the ticket? (getting into BA's WT+ is more spacious, between Y and J seating and service). If she is, maybe give her the extra to book WT+ and she'll remember when you get that choice caravan spot.
3. Is status chasing (as number_6 alluded to) important. Agree with the Plat Challenge on AA would then make sure that she is treated better once she has achieved the status and less likely to have serious problems when you aren't available to help. Would she meet the conditions of the Challenge?