Well I don't know your situation with her. Does she buy things you don't like, do you tell her not to buy them, etc? Is your expenditure going to affect bill paying, etc.? Does she monitor your money closely? I'd go for the golden silence, since from your writing she doesn't understand. I think you got some pretty good deals. Compared to me, your spending is mild. My first week of light buying (serious lights) fourteen months ago was beyond that. HDS U60, Inova T4 and Pelican M6 Lithium if I recall correctly. And lots of extra batteries!
In short, try to avoid it. If not, try to justify it. Needing more than one light if you break down on these dark Texas highways, being able to easily carry more than one, etc. You might search the CPF database/archives for member stories of really needing a light, or threads about news aritcles discussed here where people died, and might not have had a light been available on their person (In California a woman broke down on the highway, she didn't have a light on her, climbed over the barrier and fell to her death). It can be dangerous not to have a working light, and redundancy is key to seeing that you do, as is quality. I just ruined another 4D Maglite that had been in a vehicle. Batteries leaked. I put them in about a year ago, and had used the light a bit here and there even two months ago. You need more than one light, and more than one on your person, IMO.
If all these tactics fail, try convincing her to buy something she likes that you think useless!