My baby <3

A kind soul alerted me to read here. Please describe behaviors. Love this photo!

Lαrα are there any bugs on the ground when she does it?

I don't have a clue about this behavior. May be from boredom? Older dogs often lose interest in toys, but sometimes a new type of toy or chew interest can redirect their attention. More common is chewing on themselves, maybe just because of an ache or skin irritation (callous). Perhaps your dog's behaviors are a variant of this. If your dog's teeth are worn (probably so, at 11), try a canvas soft toy (supervised) or perhaps a softer chew like a pig ear. This may satisfy her enough that she won't engage in the behaviors that are disturbing you. Going under the bed may be a self-protective thing, which older dogs often adopt as a way of not having to be so vigilant as they tend to sleep more.

I'm not knowledgeable about cats. However, the idea of introducing cats to a resident mature hunting (breed) dog who has never had to cope with catitude and needs her peace seems ludicrous to me!

Not perhaps the exact same situation, but interesting comments:
www.love-springer-spaniels.com/springer-spaniel-and-cats.html
answers.yahoo.com/question/index?qid=20100522184032AAZRx3f
singletrackworld.com/forum/topic/english-springer-spaniel-will-it-eat-our-cat

Re new cuddly toy, I usually advise against these for fear of ingested fibers (from destruction of toy). But I know of two Springers who loved soft toys, and never damaged them at all so no safety risk. You know your own dog best, and sounds like a good idea for her. I am only knowledgeable about GSDs, and soft toys are most often a mistake. Had one female GSD who needed comfort of soft toy and never chewed it up.

Lαrα, relieved to hear that you decided against trying to introduce a cat! Older dogs are famous cuddlers--years of building relationship pays off in this way. I love muzzle nuzzles, and am fortunate that my pup (just 1.5 yo) is into them even as a young canine! He also loves to be hugged, and inserts himself into my pose whenever possible.

Very cute

Giving our dogs what they need...they give us so much. There is raingear for dogs if you have to go out in wet conditions (OK, England qualifies!) often. Toy may just have been the ticket to happiness. For my pup, he just shakes off wet--has very thick coat. And his comfort treat is a "chew hoof" (cow toenail, from farrier or can be bought.