AITA for being upset about how my best friend handled a trip involving my long-distance boyfriend?

I (23, F) have had a best friend for over 20 years. We grew up together and have always been close. Last year, she moved abroad for a one-year Master’s program. I visited her once during that time and met a guy who was part of her Master’s friend group. Long story short, we got into a long distance relationship. After the program ended, she and her friends each moved back to their home countries (all within Europe).
A few months later, my bf told me, that he wanted to visit one of his uni friends (I’ve met him too) in another European city for a week over NYE and his birthday, which is right after NYE. I suggested that I join him for 2 days around his birthday, not the whole trip obviously, since I understand, that he wants to spend most of the time with his friend. He liked the idea. Since my best friend is friends with both of them, I thought it’d be super fun to invite her there as well. My best friend and I live in the same city, so we could have traveled together and shared a hotel. I just needed an answer fast since it was the 20th of December already. She said she’d check her schedule and get back to me. Apparently she considered herself part of the initial plan even though she didn’t know the right dates and thought the trip would be in December. From my bf’s perspective, the original plan only included him and his friend that he visited. I don’t know all the details of what was discussed earlier.
Several days passed without any update. When we finally saw each other in person and I asked her about the plan, she told me that she had booked the trip and a hotel room for herself the day earlier (without telling me) and that she would arrive already on NYE. She explained that she wanted time alone with her friends before I arrived and didn’t want me there at the beginning because it would "change the dynamic". I was hurt and confused by this. I had been waiting for her response, and suddenly I found out she had booked without telling me and had decided when I would or wouldn’t be included, even though the trip centered around my long-distance boyfriend and his birthday. I understand, that they were friends before I met him, but it still didn’t sit right with me. I got emotional in the moment (but we didn’t fight) and later took some space to process things calmly (to avoid escalating the situation). During that time, she didn’t really reach out either, except for a Snapchat the next day asking me how I was doing. I ended up going there on my bf’s birthday, she left the same day so we didn’t see each other. When we eventually talked, she said her main issue was that I hadn’t contacted her, that she felt ignored and that I didn’t tell her I would come one day later than originally planned, "avoiding her". She insisted that she had communicated openly, that the trip had been "planned since summer", that she simply wanted time alone with her friends before I came and believes now that I handled things poorly by taking distance.

So: AITA?