My best friend got into a relationship and it feels like I lost her completely

Me and my best friend did everything together. Like genuinely everything. Same lunch table, same weekends, same person I'd text at midnight when something happened. Then she got a boyfriend four months ago and it's like she became a completely different person. Not in a bad way exactly. She seems happy. But I went from talking to her every single day to being lucky if I hear from her twice a week. The last three times I tried to make plans she either cancelled or said she was with him. I don't think she even realizes how much things have changed because from her side everything probably feels fine. I started thinking about whether I was being a bad friend for feeling this way. Like maybe I was supposed to just be happy for her and give her space to be in a relationship. But the more I thought about it the more I realized there's a difference between giving someone space to have a relationship and just completely disappearing from everyone who was there before it. I also thought about whether I was actually upset about losing time with her or whether I was scared that this was just what friendships looked like from now on every time someone got into a relationship. I realized I hadn't actually told her how I was feeling. I'd just been quietly pulling back and getting more resentful and she had no idea any of it was happening. I was expecting her to notice something she didn't know to look for. That wasn't fair to either of us. Talking it through helped me realize I'd been waiting for her to notice something she had no idea was happening. We agreed the best next step was to just tell her honestly and simply. Not a list of everything she'd cancelled, not an accusation. Just that I felt like we hadn't really been us in a while and that I missed her. That felt like something I could actually say without it turning into a whole thing. I wasn't going in expecting a big reaction or a perfect response. I just knew that saying nothing guaranteed nothing would change and I wasn't ready to let the friendship fade without at least trying.