One thought might be to explain that your directions are necessarily brief, and that it is GOOD that she is thinking about them, as people will need to think through all sorts of directions, rules, and laws throughout life. Ask HER to think about the big picture, the little details, and the fill-in-the blanks.
1- The big picture: What do your directions mean in terms of the context of what is going on? What needs to be accomplished, in order to continue with current plans and activities? What is the purpose?
2- The little details: What do your directions mean in a very specific step-wise sense? For example, if you have taught her all the steps in washing her hands, including turning off the water and hanging up the towel, then when you say "please go wash your hands now" that includes connections to all of the steps and details which she already knows, including turning off the water and hanging up the towel.
3- Fill-in-the-blanks: What blanks does she need to fill in for herself? For example, if the towel falls on the floor it is better not to hang it back up as drying one's hands with a towel that has been on the floor defeats the purpose (big picture) of hand washing... so she would fill-in-the-blanks with other lessons you have taught her, such as: deciding to take the towel to the laundry room and hang up a fresh towel.
Given this guidance and direction for her train of thought, she may begin to stay on track and use her analysis more frequently for convincing herself of the value of your directions and monitoring herself for compliance with the spirit of your directions, instead of pressing you on potential loopholes.
She may be very proud of every instance of holding herself to this higher standard and tell you all about her thought processes and her extra efforts.
