I understand that you would like to avoid any confrontation with her, but I believe the best way through this is not to ignore her but to address the issue briefly and directly:

"Ma'am? Really, how can I help you? Do you have some need? I ask because I do not understand why you approach me.

 

I have told you that I'm married, but the further truth is that I do not feel comfortable having friendly talk with you, a woman, without my wife present.

 

Thank you for understanding."

Another possibility is to let the woman see you with your wife. Is it possible that she could travel with you for a couple of days?

I understand that you would like to avoid any confrontation with her, but I believe the best way through this is not to ignore her but to address the issue briefly and directly:

"Ma'am? Really, how can I help you? Do you have some need? I ask because I do not understand why you approach me.

I have told you that I'm married, but the further truth is that I do not feel comfortable having friendly talk with you, a woman, without my wife present.

Thank you for understanding."

Another possibility is to let the woman see you with your wife. Is it possible that she could travel with you for a couple of days?