The issue with the seat swapping will be between the kids. The airline couldn’t care less unless there are spml involved but a) having observed many such groups, some kids tend to be surprisingly averse to overriding what it says on the card b) the adults in charge of the group may or may not support individual initiatives for fear of some major headaches because c) the person your daughter may want to swap with may not be interested in her assigned neighbour and more generally anything involving more than one mutually desirable clean swap can quickly become remarkably complicated especially when you start adding seat preference (yes kids have preferences too!) to neighbour preferences and size of besties group with actual seat configuration (4 friends, blocks of 3 seats etc).

in short I’d just say “I don’t know” and let her sort it out there and then.