How do I go about this...

So I have been absolute best friends with this girl Kayla for over 10 years. We met when I was 8 years old in Kindergarten and have been inseparable since! We're basically sisters.. we've been through everything together when it comes to breakups and drama and so on. now we are about to start college together! But here is my dilemma. Just a few months ago She had just came out to everyone that she is bisexual! Good for her! I was so happy for her to finally have a weight off of her shoulders with telling the world who she really is. The thing is, just a week ago while we were out at the mall she had told me shes had feelings for me for the past year. I told her I was completely blindsided by this I mean I have been in a healthy relationship with my boyfriend for over 4 years and we have a 7 week old daughter together... I told her it just would never work out between us and she knows imin a happy relationship. After that.. things got different. She wouldn't text me as much anymore and just this morning she had texted me saying "I can't be friends with you anymore it's just too hard for me"

Mind you, she has been my BESTFRIEND for 10 Years! This is so heartbreaking.. I just don't know what to do! 😢