GLaDOS is saying Caroline (Explored in the 2nd Game) is a lot like Chell. This may be true because of the conspiracy theory that Chell is the daughter of Caroline and Cave Johnson. (Explaining the fact that she has no parents and this view is reinforced by Wheatley (one of the cores that made GLaDOS do stupid things. He says that Chell has no parents and in many points of the game (Chapter 8&9) abuses her about it along with the lines (Fat, Fatty Fatty, No Parents e.t.c)