@Morihere
Well, greed is another term for selfishness so Greed was just pointing out how it's greedy (selfish) of Winry to endanger herself and her grandmother for the sake of her desired outcome.
SHE wants to stay in the country even though it will become a warzone soon because SHE wants to help the boys get their bodies back even though it will lead to her and others getting hurt or worse.
Greed points it out and Edward agrees because Ed himself was so greedy that he violated the laws of alchemy and lost his brother and half his body just so he could see his mother. Edward points to his arm signifying that he paid for his greed and because Winry has chosen a similar path, he is concerned she may pay a cosmic toll for it as well.