After you double check mom on the dimmer (without her knowing of course) and if the lights are still out check the fuse box. I don't know about the Gen1 but some cars do have a separate fuse for dash and interior lighting.
If all else fails you can easily download the entire maintenance manual, including wiring diagrams along with every technical service bulletin ever issued for mom's car
here.
It'll cost you ten bucks for several days membership but you have access to tech data for virtually every Toyota on the road today.
Cheers