Do you have any tips for coping with immature step-siblings?

Parents divorced several years ago. I'm almost 30 and my Father's GF's kids are 17 and 20. I'm close with my Dad so I like to visit but...

The 17 year old drives me UP THE WALL when I'm visiting, it is just BRUTAL to be around her. She talks non stop about every excruciating detail of her life and goes so far as to read out her current chats while we're watching a movie. When I ask her about her life she dishes all the intimate details of the drama of her 17 year old life in a very dramatic fashion.

So then we and then and like then and and and and she walks me through stories minute by minute.

When my Dad is telling me a story and she says loudly "SO AND SO JUST SAID THIS! REMARKS IN SURPRISE! DRAMATIC EXAGERRATION OF WHAT WAS SAID!"

How do I curtail this annoying behaviour?