How do you deal with people that want to make small talk with you?

How do you deal with people that want to make small talk with you? The other day I ran into this elderly lady who kept wanting to chit chat with me about everything from her cats to her garden then finally her husband. I didn't want to be rude and walk away and just kept saying "aha" or "really." So my question is how do you guys and gals handle a situation when somebody wants to strike up a conversation but you don't want to open your mouth for obvious reasons?