My best friend kept this huge secret!

Hey guys. I am in a horrible situation and I really need some advice. I just found out that my best friend of 5 years (We are 16 and in year 11 together) has had a girlfriend for 3 months and didn’t tell me about it. And not only that, she has been struggling with discovering she is bi for over a year and didn’t tell me anything about what she was going through either. I kind of feel bad that I didn’t figure it out but I totally didn’t expect her to keep something like that from me. I feel so upset and hurt that she has kept this from me for so long, and found out she told multiple people long before she finally told me on Friday, which I only think she did because our other best friend accidentally found out. I keep thinking about all the times we have talked about being single and how we need boyfriends yet she didn’t bring it up for a whole year! I want to be there for her and support her but I also want to tell her how hurt I am. I will see her at school tomorrow and I really want to talk about it but don’t know how to tell her how I feel without making it all about me. Help please!!!