I have a couple of seniors here where I had to be creative with feeding time. I stopped putting water in their food. One of them I make tiny meat balls for so that there is less mess. The other one I am hand feeding. Both of them were making a mess and didn't like face washing either so that was my solution. I use baby wipes after, but definitely way less mess. If dogs are eating canned food, they usually don't drink a lot of water. I would just keep it out for her but not force it.
I have heard that sometimes they use Anipryl for dogs with cognitive issues but I have not used it. You might ask the vet about it.
I am so sorry...I hope you can find a way to keep her happy and relaxed. Oh...and yes there are meds they can use for grooming but speak with your vet about it.
It is so hard to see them age