Yes, the kneading and drooling is normal in kittens taken away from mom too soon! I've seen it many, many times and some will continue to do this even as adults.
This is comforting for kittens, and is a habit, like a child who sucks it's thumb. It makes them feel happy and secure, hence the purring.
You can try gently distracting her when she starts, with a "Ah ah!" and with a toy or little treat. Getting her a little playmate was a good idea!
Hopefully she will grow out of it.
And as Luba says, they need to be dewormed and vet checked too.