WIBTA for reaching out after 7 years?

So me (25F) and this girl "Rosie" (25F) have known each other since we were born as our mothers used to work together. We went to school together and were best friends for years. When we were in our final year of school (aged 18) there was a big drama amongst our friend group.

One of our friends "Michael" (who would have been a closer friend of mine than he was of hers, but we were all still friends) began dating another girl in our year, "Katherine", she wouldn't have originally been a close friend of the friend group but we were all friendly with her, however we all got close when she and Michael started dating. Two or three weeks into the relationship she was trying to have sex with Michael who was a virgin and wasn't ready yet. However, a few days after this Michael found out that Katherine had an entirely different boyfriend also, who lived with her and her family.

Naturally enough, Michael, along with the rest of the friend group were shocked. I immediately cut her off and stopped speaking to her, as did Rosie. Myself and Rosie had many conversations where we were BOTH badmouthing Katherine for what she had done.

Fast forward another week or two and it was the last day of school and my entire year was going out to celebrate, everyone was drinking and having a good time, however I noticed I hadn't seen Rosie in a while, I saw her chatting and laughing with Katherine and while I was a bit disappointed, I said nothing and distanced myself from both of them that night as I didn't want to speak to Katherine.

The next day I got a text from Katherine asking me who I thought I was, I replied and said I didn't know what she was talking about. She said that Rosie had told her that I said she wasn't allowed to be friends with her anymore (which never happened).

I questioned Rosie, she didn't back up her claim that I ever said that (so she knew it was untrue) and more or less told me she didn't have time to be dealing with this since our final exams were coming up. We never cleared the air or sorted things out and that was 7 years ago.

I was devastated, I've always said that it was the worst breakup I've ever experienced and it wasn't even a relationship lol. I've always missed our friendship and wished things had gone differently.

Rosie now works for the same company as I do, but in a different location. Until today, when I am at my desk and in she walks, another member of staff who works with me (her Dad) was introducing her to everyone and when he came to me he was explaining that we knew each other forever, she was explaining to others that we went to school together and we both exchanged Hi's.

I feel all the sadness again, she has never reached out to me so I'm afraid that she might not even give the situation a second thought and may have completely moved on from it. What should I do?

WIBTA for reaching out after all this time? Should I take the fact that she never reached out as a sign?