The candles represent, quite literally, the idea of 'carrying a torch for Nostromo,' something both girls will do in Part Three, but Giselle only when she is "made to" by Nostromo; she is too "timid" to approach Nostromo before. In this sense Linda's comment is a foreshadowing.

There is also a larger symbolic meaning here regardling light as reality, in which Linda desires to force reality upon the dreamy Giselle.

Finally, "made" can also mean "fashioned," as in, "Giselle will be tempermentally fashioned to love Nostromo." (See Giselle telling Nostromo that her soul was "made for you." ) Reading allegorically, this means that utopian socialism is fashioned from a love of the People; i.e., one must believe in man's inherent goodness to advocate a society without power relationships. Conrad's highlighting of the word "made" (via Giorgio's repetition) calls attention to the double meaning.