の zaniness

Okay, I know that the particle "no" makes a noun following it into an adjective for the noun in front of it, or makes it a possessive (女友達のあんた, "your girlfriend"). But what does it mean when a conjunction (ie. "と" = "and") is put in there? For example: 女友達とのあんた or 委員長そしての仕事.

Okay, excusing my retardedness.  I pulled the first example out of my ass, but the second (委員長そしての仕事) I just read in F-ism Vol. 9, and although I can't recall another specific example, I can remember running into the same problem before.