I'm here on behalf of my neighbor, who we'll call Betty. She is a 40 year old woman and she has some issues dealing with one of her neighbors, also a woman, but who is 20 years old. Let's call her Ally. Ally doesn't live next door (or even a couple of houses away), but she routinely walks her dog around the neighborhood.
During these walks, Ally will stop and talk to Betty if she's is outside. Betty doesn't enjoy them because they're long (minimum 30 minutes, but it can go on for a couple of hours) and the topics discussed don't interest her. Ally will talk about everything and anything, like movies, tv shows, slime, schoolwork, dogs,... topics Betty finds child-like and doesn't relate to (she also finds the neighbor to be immature). Betty finds those conversations difficult and stressful. This has been going on for about a year, maybe getting progressively worse.
Betty hasn't found a way to stop or avoid those conversations. Ally seems to not be able to pick up standard social cues that indicates it's time to stop the conversation and go their separate ways. For example, Betty is in her front yard, Ally comes and talk to her. Betty stops what she's doing to talk with her, and after a while tries to put a stop to it by saying "ok, I've got to get going now" and walking away down the street, like she needs to go somewhere. Instead of going her own way, Ally follows her and continues to talk.
How can Betty elegantly show that she wants to stop the conversation and be left alone ? She wouldn't mind having short conversations, like 5 minutes (she doesn't want to be rude).
Some edits for additional clarity:
Betty has tried to make excuses to exit politely with limited success. While Betty has found some success with exiting politely, Ally then seeks out Betty's children to satisfy Ally's need to conversate and thus causing this interpersonal problem to affect not only Betty, but her children.
Betty does enjoy lengthy conversations with other neighbors, and Ally is surely be aware of that fact through observation (other neighbors who share interests of Betty are often around during Ally's arrival).
Much energy has been put into an avoidance tactic (not leaving the house when Ally is spotted, exiting politely, etc), and it has become very uncomfortable even leaving the house at times.
Ally is not an especially perceptive person.