See her somewhere, call her name, when she reacts and sees you, walk up to her and let her know. <br />
Worst case scenario she'll reject you, best case, it could be the start of something good. <br />
The thing about decisions is this, they can only be one of two things, right or wrong, but you will never know until you make them.
Test those waters slowly. I get it, but I say slowly.