Just listen politely and try to show some interest. Maybe it's important to her even if it seems pointless to you.
Well, you could nod along and give occasional responses to make her feel heard. Sometimes people just need to share, regardless of the content. Or, if you feel comfortable, you could gently steer the conversation to a more engaging topic.
I'd say be patient and don't interrupt. You never know, there might be a hidden meaning or emotion behind the story. Maybe later you'll understand why she shared it. Or, if it's really bothering you, you could politely ask if there's a specific point she wants to make.