How to enable the editor to do HTML?

Hi,

a customer of mine like to play around with different colours, sizes, unordered lists, etc.
She already has messed up all the content in Joomla after giving her the FCKEditor.

We now bargained, that she can get the BUEditor.
But it is not really comfortable and she makes mistakes like using li without ul or strong ul li /li /ul /strong.
She is not technical, no wonder that it gets messed up.

But how do you solve this?
If you have a client that likes to use all HTML options and you have to cool her down to keep a nice site.
Nevertheless I would accept ul and strong etc. from an author.

What's the best way out of this dilemma?

Thank you in advance.
Bye, Transmitter