locking just email on iphone

[lurknomore]

I seem to recall someone on here posted how you could lock just one app on your iphone, like email.  DD got onto my phone this weekend and sent a work email full of jibberish.  Awesome.  I would love to be able to just lock out my email so that she can't mess with it without having to lock down my whole phone.  Is there a way to do this?