Would that not mean jeopardising the long relationship we've had so far? Is that too big a risk, or will it be worth it?
Living life in general means taking risks. There's no way in finding out if she shares similar feelings towards you ... without showing her your proverbial hand of cards.
Is she is really your friend (and even if she doesn't share the same romantic feelings), this revelation won't kill your friendship.
Also, I hope you're not using "score" in the traditional slang manner but in a more positive innocent light. If you're basically desiring to hookup with your friend and nothing else? That's likely going to kill the friendship if the feelings are not reciprocated.