Probably some time after meals are served and trays collected, duty free is sold, etc. and maybe not fully. But why wait? Have your spouse take some ear plugs ("Hearos" do a good job with their soft rubber flanges, are cheap and widely available, and can be easily worn under the Bose NR headset she will receive if the headset isn't enough,) a sleep mask (as well as less useful ear plugs, iirc,) will be provided in her amenity kit, recline the seat, get cozy with the blanket and pillow, fade to black...

Airplane lighting etc. is for the convenience of the crew, not you - so make your own time and environment aboard the best way you can.

AA 153 Lv ORD 3 1250 Ar 1535+1 NRT 2 12:45

I'd recommend getting some snooze time, not real lengthy deep sleep -make it a very long day, light eating with no caffeine and only some napping, and arrive at Tokyo, keep active and get as much light as possible, get to bed at your usual local time, awake and get up and active with caffeine (if you normally use it) and breakfast at your usual local time to minimize jet lag.

IMO, getting lengthy sleep on this flight means she will have a battle sleeping well the first night on the ground and will prolong acclimatization to the new time zone. YMMV, but this has worked well for me over the last 40+ years I have been traveling to Japan.