That sounds like tough issue.
So it doesn’t, at first glance or even on inspection, look like anything provocative. Just a black cube, some plugs, hose, power cable and other connecting parts and a receiver. It kind of looks like an old school version of a C-PAP machine.
So just get this thing, set it on your night stand, next to the bed, with everything ready to go. When she asks what it is tell her, “Hun that is my CPAP machine to help me with my Obstructive Sleep Apnea.” This should help me sleep better and hopefully I’ll quit snoring. Then she’ll hug you for being so thoughtful.
Then when you lay down at night put that receiver over your nose and turn it on to a respiratory setting speed. When she’s not looking or asleep, whip that thing under the covers and put it on were it belongs and go to town. She’ll never know…seriously.