OP,
I found the info here helpful. There are also lots of recipes.
https://www.dietdoctor.com/high-protein
When my mom was in a similar situation and got tired of eggs or meat she would happily eat this topped with berries. I'd add 1 whole additional egg for the nutrients. Sometimes I'd make it with 1 c canned pumpkin instead of a banana.
You can add things like vanilla, pumpkin pie spice or cinnamon. You can also top with some vanilla Greek yogurt or a little cottage cheese under the berries. It's also good with some chopped sauteed apples, cinnamon and walnuts or pecans. When we had chocolate whey I added a zucchini to the blender instead of the banana for chocolate zucchini pancakes, with added chopped walnuts. I usually double the recipe for the family and sometimes use 1 scoop unflavored and 1 scoop flavored whey. With some chicken sausage or turkey or Canadian bacon on the side it really ups the protein for the day.
https://twitter.com/tednaiman/status/1378413112844382208
For simplicity and to save time we do "scrambled style" pancakes"
https://www.instructables.com/How-to-Make-Scrambled-Pancakes/
I add extra boxed whites to scrambled eggs, omelets, frittatas and used if for the pancakes, it all adds up.
My mom was able to regain then maintain muscle in her 90s after a period of bedrest, despite kidney disease, with the combo of doctor instructed increased protein and PT, then gym time. It takes time and consistency but it really did work, despite the idea that older folks can't gain muscle.
Older people don't process protein as well so I was told to focus more on animal proteins along with increased amount. I'm not a huge processed food person but some whey powder can help, both with reaching the leucine threshold and because liquid calories are not as satiating. I divided the drinks, like you said you were thinking of doing, or she would not eat, saying she was full.
My mom was not on an appetite suppressant and it was still not that easy to get her to eat and eat enough protein, so my heart goes out to you. Your relative is lucky to have you and DH, you sound like lovely, caring people. Don't forget to go for walks, do yoga or whatever is stress relieving for you. As a caregiver don't forget your own oxygen mask. Hope your loved one is on the mend very soon!