Grandma's not wrong ... about the bags. 5k for a 7-day cruise, spread out over two or (more likely) four people, gets you an interior room with the bare legal minimum of clearance around the furniture, and a teeny-weenie closet. Large bags may not physically be an option for their booking.

Her everything else is terrible, though. Leveraging cost, showing up (unannounced?) to supervise packing, plus all the missing details everyone else has speculated over (did she book the cruise for dates during the school year?) -- YIKES.