There could be several reasons why this older lady behaves differently when she comes into the store alone versus when she comes with her husband:
Social Dynamics: People often behave differently in social settings depending on who they are with. When she's alone, she may feel more at ease and comfortable striking up a conversation with you. However, when she's with her husband, she might prioritize their interaction and be more reserved with others.
Personality: Different people have varying levels of comfort with social interactions. It's possible that she is naturally more outgoing when alone but feels more reserved or shy when in the presence of her husband.
Marital Dynamics: In some relationships, one partner may take on a more dominant or leading role in social situations, while the other partner prefers to take a back seat. Her husband might be more extroverted or take charge in social settings, leading her to be less forthcoming.
Privacy: The lady might also be more cautious about engaging in conversations when her husband is present to respect their privacy and the dynamics of their relationship.
Age Gap: The age gap between you and the lady could also influence her behavior. She might feel more at ease talking with someone closer to her own age but might hold back a bit when interacting with a younger person.
Cultural Norms: Cultural norms and expectations can also influence how people behave in public, especially when they are with their spouses. Some cultures may emphasize more reserved behavior in public settings.
Personal Comfort: It's possible that she simply feels more comfortable talking to you when she is alone, as there might be fewer distractions or social pressures.
Remember that people's behavior can be influenced by numerous factors, and it's not uncommon for individuals to act differently in various social contexts. If she continues to be friendly and willing to chat with you when she comes alone, it's a positive indication that she enjoys the interactions with you. Respect her boundaries and interactions, and let the conversation flow naturally based on her comfort level.