My linnies do their beak care by themselves.
Does Kissy have natural branches with bark for nibbling?
If you can't get them from nature you could also buy something like this.
Does she use a rough mineral block?
I feel like she has been molting since November, she always has pins on her head
She has no linnie partner to open the pins, solitary kept linnies often look like that.
Have you always found many feathers on the cage floor since November?
A few ones are normal, but if she is molting permanently you can buy her a bird lamp, that brings her hormons in order.
Her beak is also crooked (and has a bruise/cut that is healing from her falling in her cage, which happens a lot)
Kissy needs a soft bird safe cage litter. I know hemp litter is not easily available in the USA, but what about aspen bedding?
Did you put away the grille from the cage floor?