If it's to do with control then I'd recommend learning some aerobatics. It'll build a huge amount of confidence and make 'normal' manoeuvres not seem quite so bad.
If it's to do with navigation then I'd recommend getting a GPS as a backup and not flying when the conditions are marginal until well practised.
If it's to do with communicating with ATC then I'd recommend just practise.
Good luck to your friend.