Do I tell my best friend I’m in love with her

So I’m aware this is a cannon event but… unfortunately I’ve fallen down said cannon.

I’ve known my best friend for roughly four years and realised I was in love with her back January but I didn’t say anything because she had a boyfriend and I wasn’t gonna get in the middle of that. She and him broke up and she said she was checked out of that relationship long before that. At the time, I told myself I would tell her if she and him broke up.

Now, I’m not sure. I’m second guessing everything. Is it selfish if I tell her? I don’t think it’d break the friendship but I’m aware it could fracture it.

I’m just scared I’ll be essentially isolating her from her best friend if I tell her, and I’ve been her rock for the four years I’ve known her.

I wouldn’t be telling her to get a romantic relationship, even though she likes girls too. It would honestly just be to talk it through and try to work through this because she’s the person I tell everything but I’m scared I’m being selfish if I tell her.