My 10 year old cocker spaniel has gone off food and is hardly drinking.

My 10 year old female English Cocker spaniel has gone off food suddenly. This has gone on for 4 days. She is normally very food-orientated but is barely eating. I've been making up chicken with rice in a light broth but I'm resorting to giving her a little by hand which she'll take a little of, then she gives up. She is barely drinking water since yesterday and I've been cradling a little in my palms which she'll lick. She is very lethargic and sleeping a lot at the moment. It's strange though that the last few days since this has happened she still wants to go for a walk and will chase her balls so I thought she would improve but once she's back at the house becomes lethargic again. I noticed also her gums are quite pale. I will take her to the vet in the morning but should I call for an emergency vet today?

Hello and yes - please call for an emergency vet.  Pale gums and being off food / drinking and lethargic are all serious signs and could amount to an emergency.