She's going on a trip with her choirmates.

The Party intellectual knows in which direction his memories must be altered; he therefore knows that he is playing tricks with reality; but by the exercise of DOUBLETHINK he also satisfies himself that reality is not violated. The process has to be conscious, or it would not be carried out with sufficient precision, but it also has to be unconscious, or it would bring with it a feeling of falsity and hence of guilt.

But till I am thirty, I know that my youth will triumph over everything- every disillusionment, every disgust with life.

In these terms, Ten/Rose has a highly privileged position among Doctor Who pairings, and it seems that this position exactly engenders a powerful resistance to it among non-shippers.