What time of the year?
Late June - fly to anchorage and drive north to Denali. Come back after a few days and go south from anchorage to Seward and take a day cruise to see glaciers.

Any time during the summer - Bar Harbor, Maine. There are numerous coastal towns that are beautiful.

Astoria, Oregon and coastal Pacific region of OR and WA are incredible.

Yellowstone AFTER school starts back in September.

If she is more inclined to cities and shopping, NYC on Memorial Day or Labor Day weekend is the time to go. The locals all leave town. I saw the Mets and Yankees at home and no issues getting cabs.

Boston has been my favorite big city.

Fall colors in New England