dd's red "bits"

[bagpussmice]

dd1 is 5 and seems to have a constantly red bottom both front and back. she says it feels sore, esp. in the evening. we are very scrupulous about cleaning after the loo, obviously I can't help when she is at school, but have stressed how important it is...
she says it feels like it's sticking together and feels uncomfortable. it just looks dry and red.
what can I do and what can it be?

fatfox, thats what I thought re wipes - will go back to non-flushables, sounds sensible anyway plumber-wise.
Sorry for multiple posts, have head stuffed with cold this morning and not thinking fast enough...