She's either dishonest or dumb (or both). She doesn't really mind if we think she is dishonest. But she'd be annoyed if people stopped calling her the Smartest Woman in the World.
In short, she provides a ridiculous story about how Bill fooled her -- and she hopes that we simply wink at it and say "She's lying, but we undertand."
Underlying purpose: A spouse cannot be forced to testify against a spouse--as long as the marriage is still valid.
Hillary did and will continue to "overlook" Bill's "indiscretions".