What should I do when my bestfriend is caught between me and her boyfriend?

Whoa that a tough situation, I was in that same situation a while back with 1 of my close friends who is like a sister to me. We've known each other for 10 yrs, when she started acting like that I just didn't tell here things I normally would and I didn't call her as much. When she noticed I wasn't calling as much she started calling me and in turns of me telling her my business she was the 1 spilling her guts. So it was kind of like the tables had turned because I started hanging out with other friends and I guess she picked up on that. But we're still close till this very day. Its kind of like that old saying you never miss your water until your well runs dry. She noticed that her bff wasn't around so she put forth the effort and started reaching out to me. But most friends go through those changes when their in a new relationship, give her some time to come down from her high, but in the mean time hang out with some new/old buds of yours and don't tell your bff any of your secrets until you feel you can trust her with them like old times.