I don't know what you should do, it's up to you and what you think is best since you do know her better than us. Sounds like you've known each other for a while, do you know her patterns? I say that without thinking myself, I figure if you know her well enough she might somehow think of you less than a brother and more like a new kind of friend, one that may have further developments, know what I mean?
I've sorta been through this before, except I knew she was pretty from the very start, a friend told me you don't know until you try, I wish I didn't.
One thing for certain, girls aren't stupid, for all you know she is very well aware that you may have got feelings for her. She may wonder why you haven't said anything or hope that you wont -- that depend on what kind of friend you are to her.
Think about this, or try to even if it hurts: Imagine what it would be like if you told her and nothing worked out and you weren't friends anymore, not that that would happen, but unless you really know her, you got to prepare yourself for anything.
Don't do anything now, yeah it's been 8 months, just think if you decided to tell her at that moment, it probably would have been bad. Give it some time. If you really want to do something, though I would suggest it unless you think she wouldn't mind, flirt. Smile and look into her eyes more, be more kind, be there for her, talk to her. If you say a bunch of "uh's" or stutter then she's got you figured out.
This is all I can say now, I'll just end up thinking about my problems and end up giving you a biased response.
The meaning of life is curiosity; we were put on this planet to explore opportunities.