Not OP but been thru this a ton of times cause I love dogs more than humans 😄. I dunno if you’re gonna get a good answer here. Every situation is different, every person is different, and every dog is different. The best way I’ve been able to describe knowing when it’s time is simply when it pains me to see my little dude/dudette just simply live. If they struggle just to get up each day or can’t eat without vomiting or any number of maladies that make living more of an ordeal than I’m comfortable putting them thru, it’s time. Life shouldn’t be a punishment, especially for those little bundles of pure happiness. Its terrible and it’s incredibly hard but I think most people end up just instinctively knowing the moment. Dogs (and even the few cats I’ve had) have a unique bond with their owners I think, and when that bond is strained to the point of breaking, you can just sorta feel it. Course, like I said, everyone is different and approaches the situation differently. Unfortunately i don’t think there’s an easy answer. For what it’s worth, just from the sound of it, it seems to me like Delia has some fight in her yet and still enjoys her days.