These therapeutic lies are quite humane. There is NO need to keep reminding the person with dementia that their spouse is dead and have them get upset and grieve over and over again. Some great suggestions for how to respond with something vague that is not so upsetting. If she doesn't remember now, she will likely never remember and that's OK.
I've mentioned this same scenario of a friend's MIL who constantly asked where her deceased husband was. At first they'd tell her he was in Heaven, but that made her cry each and every time, like it was the first time she heard the news (and with her dementia, I suppose that's how it was to her).
So, he is now "at work" or "had to go to the store". She doesn't remember the answers of course, so she'd ask all day long. But she no longer got upset at the answers, and that helped immensely.
Try using D-Mannose for the UTI. Supplement comes in big capsules, one a day, easily broken and added to food. Works a bit like cranberry, keeping ecoli from adhering to the bladder wall. Check on the UTI as it causes mental changes. As far as the asking after someone just rote little NON-argumentative things with diversion. Such as "You miss him when he isn't here, don't you", or "I wonder what he is up to" or "He has such good ideas for us, doesn't he" or "Remember how you two watch Judge Judy all the time" or " What was his favorite dish? Was it lasagna he liked?" Provide pictures. Make memory books. Talk about him as though he is around in the next room, but divert away after a brief statement. Sometimes nothing at all will work. If question becomes When will he be here sort of thing then it is "I am not sure". Or "I think soon". "Remember he is fishing". Just those therapeutic fibs. Good luck.
So, he is now "at work" or "had to go to the store". She doesn't remember the answers of course, so she'd ask all day long. But she no longer got upset at the answers, and that helped immensely.