a plush doll

The body is easier, as any alterations to make it easier to exist can be done side-by-side with ones to reinforce its inanimate existence. Give it a cane so it can move around with less pain and discomfort? Replace its legs with limbs of an appropriate material that still need the cane, but won't cause pain or discomfort. Any upgrade made can go very nicely with one to push it deeper into dollhood.

Now the mind? That's where the fun truly begins. There's the route of classical training, where it associates rewards (whether praise, stillness, or treats) with a specific action. Snapping ones fingers can eventually, with enough rewards, help derail a dolls negative thinking into pleasure. With enough careful tinkering directly with its mind, you can even alter its words and thoughts. Replace its ability to apologize for existing with "This one is a good doll, and it loves itself." Prune its ability to hurt itself by overworking. Shatter its mind to nothingness and create it anew according to your vision.

bite me!

go die

get off me you creep

wait stop

no please