"...but she could not deny the feelings they'd stirred or the dangerous question such feelings raised"
Even though his gestures where small, they still gave her a little thrill inside. To stir your feelings is like stirring soup, all kinds of things float up to the surface. In this case "questions" were "raised" up in her mind. Probably questions like "does he love me?" or "do I love him?". She considers these questions to be dangerous.
So yet again the woman in this story is trying to understand how she feels about this man. I'll assume this is Elizabeth and Adrian from the book Redemption Road.
These two people obviously like and admire each other but they can't seem to figure out what they mean to each other. The people reading the book probably want them to be a couple and get married and live happily ever after, but that's not a very exciting story so the author keeps everyone in suspense by keeping them apart (until the very end of the book I suppose).
"Yet even when she was a cop herself, he'd maintained an aloofness"
To act "aloof" means to not be friendly. It means to be a little cold and distant to the people around you. It means you have the opinion that you are better then other people. Perhaps this feeling would be understandable if he was a cop and she wasn't, but she is saying that he maintained this attitude of aloofness even when they were both cops. What a jerk!