It's bad for business

When Jessa went to the women's boutique, she quickly came out because of the price tag on the mannequin. She caught Allison going to the other stall. Hence, she went to another one to check if there was something she could buy for her husband. 

After minutes, Jessa realized nothing could suit her husband here. Thus, she went to the stall where Allison was. She didn't plan to get inside and simply thought of what task she would give the children to keep them busy after exam week. 

While idling, she heard Mrs. Miller's voice. That woman's voice was so loud that even Jessa, who was outside, could hear everything. She didn't plan to interfere, since she was curious about how Allison would deal with it. Much to her disappointment, Allison backed down and chose the peaceful route. 

That didn't sit well with Jessa. 

People like Mrs. Miller were worthy of all the pettiness in this world.