why is she scared? For me personally, the best thing is to take a hot bath together... slip into some lingerie and lay in front of the fire.. Can I ask what you do to turn her on? maybe if you get her really going she won't lay there like a wet rag.. lol..
What kind of feedback is she getting? If she used to be adventurous but then stopped, it might be because she got some feedback letting her know that her adventurousness was unwelcome. Consistent, regular encouragement could reverse that process.