I don't think chickens "have to have" companionship of another chicken unless they are treated as "regular chickens". If they're raised in a house with a human being as constant companionship it's a different situation than a chicken left outside in a coop by themselves 24/7...entirely different. A flock need not consist of chickens...it can consist of 1 chicken, 1 dog, and 1 guinea pig who all adore each other. It can also consist of 1 chicken and 1 human with daily interaction. It depends on how much time you have on your hands to spend with her.
There are many people with only 1 indoor pet chicken and the chickens are perfectly happy...you don't "need" another chicken to keep it company in a situation like yours.
People say the same thing about parakeets and ours is perfectly happy by herself - with free range of the entire house. Her only issue is perch humping due to no "mate", but that is a hormonal reaction and not an emotional need; she's a very delightful and happy bird.
To answer your question you asked and nobody has answered yet - the pellet form of Feline Fresh is fine for chickens. The clumping form of Feline Fresh is not fine, because it can and will accumulate and clump inside their crop, causing serious impaction. Per Dr. Arelan - board certified veterinary surgeon.
I would advise against either one, but only because they are for cats, not chickens. I'd stick with a mix of pine shavings, DE and Sweet PDZ.
Whatever you decide to do I'm sure your pet Silkie is perfectly happy just being with you, and thank you for sharing a picture with us!