One of the other guys would probably give you a much better answer, but since you asked …
Getting lovers, both casual and serious, has never been a problem for me, but making good friends always has. I don’t trust easily. I am heavily biased towards keeping the friendship going, even at the expense of a possible relationship. So bear that in mind when you read this.
The important thing here is what she wants and needs, not what you do. The lady comes first does not only apply in the bedroom, but in day to day life too. You need to find out what she feels. And accept it. If she is interested too, great! If not, also great – you know and can pursue someone else knowing she is cheering you on and has your back!
You can beat your brains out analysing her every word and gesture, to your intense frustration as no one has made a guy/gal translation ap yet, or you can simply ask her. Sounds risky, but not if you do it right.
Be honest with yourself first though. Are you interested because she is available, or is she someone that you could seriously spend you life with? Remember, no pressure on her either way at all. Friends don’t do that crap unless it is needed, and in this case, it isn’t needed. You really do want to stay friends, no matter what.
Last time this happened to me, I asked her in the negative, as it has less risk. Out for a meal – we were very close friends, like holding the head over the toilet to throw up close – and I just said “We’d make a terrible couple, you know.” She smiled and said “Oh, I don’t know about that.” We’ve been together for a while now. So it can work. Sometimes.
Good luck to you.