Actually, the OEM switch is vacuum actuated, and that is why it's not happening. The Atlas doesn't have the vacuum switch needed to shift the axle and put vacuum to the light switch. Therefore, you will have an easier time with a mechanical solution - and it will stay cleaner and easier to service, since it's in the cabin.
Oh - do what I did. Buy her her own Jeep (my wife drives an XJ as well, and it's a touch newer than my two...)
Anyhow, I'd need pix of where the levers come thru the tunnel with the console open. I don't know what sort of space you have available, which is why I need to see the installation...
5-90