I realize that it is acceptable to mix past perfect with simple past. The event described by the past perfect happened first in time. Examples:
She had never seen a bear before she moved to Alaska.
The thief had spent the money when the police caught him.
I watched television after I had finished the dishes.
In summary, I don't think there is a difference in meaning between
past perfect + simple past and
past perfect + past perfect. If anyone can point out a difference, please let us know. I think the following sentences are equal.
She had never seen a bear before she moved to Alaska.
She had never seen a bear before she had moved to Alaska.