Getting rid of a close friend at lunch so I can hang with my other closer friends

Hi Guys,
I am having a serious problem. I have a group of friends that I always hang out with at lunch. My best friend is in this group and we would always sit next to each other. Then a close friend tagged along in our group because she fell out with her friends and she had no one else to sit with. HOWEVER my friendship group does NOT like this friend that started tagging along and the close friend isn't taking the hint and continues to tag along. My best friend whom I used to sit next to, now doesn't sit next to me anymore because this close friend does. I am losing my strong connection with the friend group because of her. How do I get rid of her without ending our friendship, she doesn't have anyone else to sit with at lunch that's the problem, so I will be just leaving her in the dust. Help me break it to her nicely pleaseeeeee, I want my best friend back.