I guess there's some excitement to the idea of telling her, even though I wouldn't be taking action.
My problem with telling her is wondering if she would be offended.
Let me get this straight you would like to tell her just to see her reaction only and if she would indicate that she has sexual feelings toward you also you would take no actions of any kind?
Kind of like getting a phone number from a woman even if you have no plans of using it just to see if you could get that number?
Ok kind of a strange way to act around a family member you have a long term relationship with in my opinion.