Well, your best friends right? Then you two should be able to talk about anything and everything. Real friends tell each other things, whether they like it or not especially if its in their best intererest. Explain to your best friend that you don't like the way they are acting and something should be done about it. As best friends, you will discover that it will be ups and downs and even arguments you may get into which may be a little crazy and when you'll both look back on what the argument was about, you realize that it was just a waste of time. Life is too short to be worried over pety things. So when you talk to your best friend, be straight forward and hopefully you'll will come to a compromise.