How Can Tell My Friend To Stop?

She's does literally about 10 times a week. All you ever hear her say is "My sister is a double D! Can you believe it? She's I'm going to be just like her! She's only 16! We have to buy bras from Victoria Secrets and buy those are expensive!" How can I tell her in a nice way to stop talking about her sisters bra size! It's so annoying!