I agree, continue to be nice but give her some space. It is her turn to make a move when and if she feels that way inclined.
The brother thing, yeah well, I dont know how old either of you are. But I did that in my bit younger days.

My ex broke up with me in a not very pleasant manner, so I slept with his brother......sooo immature. His brother and I were mates previously and continue to be so, but I felt bad that I used him like that (not that he was complaining

).
I think its natural for her to avoid you at this stage, you DONT want to be getting involved with her just now if you really want this to work. Nothing worse than filling the void of a broken heart, to have the broken hearted mend and realise they "thank you for your time, but bye now, I'm all better".
Good Luck - you've been a great friend to her and I hope she appreciates it.