Hmm, with a Service Dog in Training, that does make it more difficult. I have multiple dogs/pets as well, but none for Service Work.
What 'I' do with mine is make sure when I get home from work is to greet everyone by name - even when I get mobbed at the door I make sure to single out each and every one. I make excuses to take at least one guy with me where ever I can, even if it's just a walk to the mailbox or out to feed chickens. I have one that likes to ride the lawn mower with me (he's a toy poodle) but doesn't like car rides - go figure. So, Turner 'mows' the yard, while the dogs that like car rides will go with me to feed the mare (she lives 1.4 miles away lol). I take turns on who goes to the feed store and who stays home with a fresh raw bone.
I do have a large fenced back yard so I can also allow them to run while I call individuals back for treats and send them out again. (good recall training and it singles them out to make them feel noticed/special lol)
I don't think it's necessarily the amount of time you spend, but the quality of time. I also make an effort to spend multiple times per beastie each day for one on one time, even if only for 5-10 minutes, but several times a day - like when OB training a pup.
Your mature girl would probably appreciate the one on one time just to walk to the mailbox and get a treat, maybe learn an easy new trick (keeps mind active), sneak a cuddle session in for just the two of you. Maybe an extra 5 minutes of 'special grooming' time - I have one that I sneak in grooming with play because she HATES brushing, she gets petted with a brush while chasing/tugging a toy.
Just get creative and stop feeling guilty. Make the time you do have for her and just her very special, even if it seems too short.