How long to ask out a coworker?

gemgem
So there's this girl took a job where I work about 3 weeks ago. We don't work together, but I see her occasionally (like every 2,3 days) and we talk for a few minutes. Usually we don't have time for an extended conversation because she is busy, but she gives me a lot of signs of attraction when we talk. Also, her brother is a friend of mine and he has hinted that she is interested in me. So, I have already made up my mind that I want to date her, but I wonder if it is too soon and we don't know each other well enough. Since we are coworkers should I take things a bit slower, because we will definitely be seeing more of each other at work? I mean the total length of time we have talked is maybe 20, 25 minutes over 2 weeks, that doesn't seem like very much time and I don't want to seem desperate or too aggressive.

guys, would you ask this chick out now or wait? Girls, would you want to be asked out in these circumstances? How soon is too soon, and how long do you think will be too long?
Updates
+1 y
She quit. :(
How long to ask out a coworker?
2 Opinion