The process consists of reviewing all financial transactions that occurred during the year to make sure they were entered correctly: checks written, bank statements, deposit slips, etc. Even if you have the world's greatest treasurer, you should have an audit. Thousands of dollars likely move in and out of your account during the year; it's very important to double-check that those transactions were recorded properly.
For more details on running an audit, putting financial controls into place, and managing your finances, these articles on ptotoday.com are a good resource:
Protecting your money is the responsibility of the entire board. Your treasurer puts in a lot of hours managing that money. Give her the support and your members the peace of mind of this important backup system.