Am I really selfish?

People told me I am selfish and wrong because I got upset that my ex best friend is trying out for basketball cheer and I said I don’t want her to because cheerleading is my thing... I understand I don’t own it but cheering is my thing and it’s what makes me happy her thing is more of hunting and fishing. I understand how it makes me look selfish but I kinda feel like everyone has their own thing and cheering is mine and she’s taking it from me. I want to be happy for her but I’ve just been talking about doing basketball cheer for soo long now and then she randomly just out of nowhere says I’m doing it too. It was kinda something I wanted to do by myself but I didn’t tell her that.... does that make me a bad person?