hookers & blow?
or is it too soon...???
I'm just sayin...I'm a hookers & blow kinda guy, so uh...yup
Seriously though, if you stay close to the place where you 2 met, take her there, and talk about how she's made your life better. Reflect on how the relationship you 2 have built has brought you joy. After 3 years, I'm sure there have been times where after a DIFFICULT day, seeing her again was soothing for the soul. Let her know how much you appreciate her just being a part of your life.
But remember, the deeper you go, the deeper she's gonna think. If you want to marry this girl, man up, and put a ring on it.