RE: It is my third time, her second.
Are both of you vaccinated and boosted?
Nope. Natural immunity from getting COVID is broader and lasts longer than immunity from the vaccine.
Natural immunity lasted over a year and a half for me between infections and each time I have gotten it the symptoms have been milder than the last time. Meanwhile, everyone that I know who got the vaccine and didn't die from it (I know two who did) got infected within 6 months of the second shot and had worse symptoms than I did.