Never noticed anything like that before do you happen to work at one of those nail salons? Do you have a photo of this lump of skin that you speak of? Again it could be a few that you saw but I wouldn't say all chinese girls have lumps of skin on their toes....you should rephrase the question to why does this particular chinese girl have a lump of skin on her toe or something similiar.

For the same reasons some western

(hate the term western in this case.
doesn't mean the Dominica Republic isn't western because is a bit poorer?)

women have them all over the world including males..no "sexual preferences"
I'm afraid in this case....
one
http://health.nytimes.com/health/guides/symptoms/skin-lumps/overview.html
two
http://ehealthforum.com/health/lump-with-two-black-dots-on-left-big-toe-t345041.html
 

Need more? just ask...
 

The constantly peeling skin is due to mercury poisoning.

Do you mean a callus? (or possibly corns?) Everyone gets them, not just women...

They are caused by wearing shoes that are too tight.

if you mean on the tops of the toes its from wearing high heels.  i asked my gf about it and she only gets them if she wear high heels

I haven't noticed any lumps on toes, I'm more of a leg man. Have you seen any webbed toes?