Well, with all due respect, asking how much it costs to rent an apartment in NYC (even if you limit yourself to Brooklyn) is even more ridiculous than asking how much it costs to rent an apartment in LA. Without knowing more about your budget and your needs, it's an impossible question to answer.

What is your friend's budget? What will she be doing in the city? Is she working or going to school? Where? Are their other parts of the city that she will be going to regularly? We need a lot more information before we can provide any information that will be remotely useful. Right now we're up to 8 posts and all we've done is wasted bandwidth.