Coworker/work friend confessed feelings for me and idk what to do.

I have a coworker who is definitely my best work friend, and they’ve become my friend outside of work as well. we don’t hang out outside of work really, but we’ve visited each other if one of us was off and the other was on type of thing, and we text a lot. I suspected they were into me but I didn’t say anything bc I don’t want to assume and make a good friendship awkward. Well I was telling them about this guy I met, and they got really weird and short with me, and then told me they thought I was cute and that’s why they were upset. Idk how to turn her down, and have it not be weird. it’s not even like we work the same department, we literally work side by side all day, and I also want to keep her as a friend. Any of y’all deal with this? What do you say? They make front end bearable I don’t want to fuck this up