Personality changes in chickens aren't uncommon at all. Lots of things can change behavior. I've had some pretty dramatic personality changes in my flock. For instance, one Brahma hen was always very timid and was always bullied and picked on by the others. She was bald for much of her early life. Then I decided to keep her separate so her feathers could grow back, and after a couple months of this, she returned to the flock with amazing, new-found self confidence, and to this day, she now stands up for herself.
Some hens are more in need of human attention than others. Some come to be addicted to being held and cuddled. Recently, a couple of older Wyandottes that have always hated to be touched now act much like your pullet, suddenly craving attention and affection. Today, another Wyandotte, who has always pecked me when I go to touch her, has suddenly begun to hover closely when I'm showing attention to the others. I reached over and brought her in close for a cuddle, and she submitted to it for the first time in her four years of life, even to the point of relaxing and almost falling asleep.
Some people mistake a hen coming up behind them and pecking them on the legs as aggression. Most of the time this is a signal that this hen wants you to show her some attention. Even my rooster does this when he wants a hug. It's just a gentle tapping, and is in no way aggressive. When I bend down and draw him in for a hug, he melts into my arms and almost falls over in ecstasy.
Chickens can be among the most affectionate of all animals if only people paid attention to their signals.