[20F] I'm telling my best friend I have feelings for her this weekend

So I have been struggling with this for a while. I'm not out as bi to anyone really, although it is something I have discussed with this friend, and I know she is in a similar spot. I've had feelings for her for a while now and just began to acknowledge this for myself. She is in a relationship, albeit a shaky one, so I know this may be an ethical gray area, but I know I need to do this so I can move on (or not, depending). The not knowing has caused me so much anguish. So I'm telling her at some point this weekend. And I'm definitely not freaking out about it. Nope. Not at all.