Yeah, you've probably been discussed with several other sisters at the hall. Having a bible study gets them very excited. Mostly because there isn't many of the general public that will study with them.
So if you stopped studying with them, your conductor wants help in finding you home. So other witnesses if they are in the area, know about you and want to "encourage" you. If you had shown a greater interest in the sister that smiled at you, she may well have gotten out of her car to talk to you.
If you don't want them to pursue you, sometimes just saying no, might work. But then, your conductor will probably keep you in mind and stop in occasionally to try to convince you to study again. If you do a little research into the Australian Royal Commission case 29 Jehohvahs Witnesses on youtube, you will see how the JW organization doesn't report child sexual abuse to the police. Which lets the pedophile have the opportunity to molest again in the congregation, as well as children in the neighborhood - all without the police or the parents knowing.