Teatree oil is good for that sort of thing. If the pimples are on her nose she should scrub with a flannel. An exfoliator won't be good if she has a break out as this just makes it worse. Failing that, drinking lots of water helps.
My daughter is 10 1/2 and very 'hormonal' (mood swings, body developing, greasy hair,etc) Over the past few weeks a few pimples/spots have been developing on her face - I've made light of it ,but she is understandably self conscious (especially as few children her own age are going through this yet). I've bought some 'oil free' face wash but don't know if this is appropriate for young skin or is even making it worse! Any suggestions would be appreciated!!