I can place it precisely. She is Enid Loopner from the old Saturday Night Live sketch, Lisa Loopner’s mother. If you can find the refrigerator repairman skit video, Jane Curtin (Mrs. Loopner) even has her hair done like Mrs. Palin’s hair. It might be here: http://www.hulu.com/watch/4112/saturday-night-live-nerds-broken-fridge
I had the same thought, especially when she says "TAAAAWD". It's a cute accent and fits her bubbly personality,and it's definitely more Upper Western Great Lakes than anything else.