My 2 best friends are bi and I'm kind of confused?

Hey, so, my 2 best friends, lets call them 'Kelly' and 'Cathy', have recently come out to me that they're bi. Kelly texted me about it first and I said 'oh, umm... okayy' and that was a few weeks ago. We've been fine, still the best of friends. However, a few nights ago Cathy texted me and was like 'I think Im in love with Kelly'. I had no clue that she was even bi, much less had a crush on Kelly. So, I'm completely confused, and I need to know what to do...