Hi, the purple kitten is not a Lady lovely Locks kitten, but a pretty little kitty (more related to MLP then LLL) Most easily recognizable by the cutie mark, which the LLL cats don't have. Also, the LLL cat will have TCFC or "those characters from cleveland" printed somewhere, like the dolls and the horse. The pretty little kitty was made by hasbro, i believe.
The white cat is worth 10-30 I think, it depends on how many people are looking for her. The white one is somewhat rarer then the others if she's really white, not turned creamy.
Her name is Curly Kittens Creamy Coat
The purple one, no idea, since it's not LLL related.
3-4 on the common pixietail is an ok price. The comb gnomes (of Ravenwaves) or butterflies can go higher.
Silkymane is in a poor state, anything you get for her is fine if you ask me.
Good luck on selling!