You ask: "Why a single woman is more under scrutiny in the JW religion; and if there is a way to keep them out of your business or will they find out anyway."
In my opinion, a single woman is a sexual threat and not just in the JW religion either. That is just the way it IS and you have to deal with it.
As far as keeping Witnesses out of your business: sooner or later everybody's general story will become known, even if you didn't bother much with anybody...It is the same everywhere, even on a job.
However, there is a big difference between having your "general" story known versus answering intimate questions that are really nobody's business (such as your financial status or personal romantic questions).
There is no getting away from this in the religion except limiting your contact with certain nosy people. Keep your lip buttoned at gatherings and limit alcohol intake as it is like "truth serum".
In some instances, you WILL have to say "that is nobody's business" or "I don't discuss things like that" and turn away from the offending person.
Don't be afraid of being vocal when it is necessary.
And, by the way, the Witnesses will try to separate you from your family and non-Witness friends...Don't let this happen! You will reach a point where you will be grateful you can turn to them!