Why doesn't she just say 'no'?

So, every week I go to another city just for one day. I work remotely. Two weeks ago, I saw a girl at the metro station, and we made eye contact. Unfortunately, her train arrived, she got on, and as the train stopped before leaving, I gave her a small smile. I felt like I had lost her. But then, this week, at the same time, same place, and in the same chair (for luck purposes, XD), the moment began. I saw her from the window, but I acted as if I hadn't seen her. Then, at the exact moment when she noticed me, we both started laughing. I thought this was my last moment and last chance. I have never approached a girl in public before, and I don't have a girlfriend. I started using my phone just to remove some apps before going to her because sometimes my phone lags, haha. Then I went to her and said, 'Hi.' We shook hands, and she was beautiful ,I asked for her name, and then I asked if she could provide any contact to reach her. She wrote her Instagram username in my notes app. For the first time, my phone was alive and working fine, XD. Then my train arrived, and I said goodbye. Here's the problem: I don't have Instagram, and I feel awful. So, I tried to revive my old Instagram account that I last used during the COVID time. It had 10 followers. I started following some people hoping they would follow me back. However, I didn't send her a message because her Instagram account is private with a beautiful profile picture. I made some changes to my account, added a bio, and today was the fourth day. I followed her, but she hasn't accepted yet. I think it might be because I don't have a profile picture. Then I added a profile picture. Now, after 12 hours, she still hasn't accepted my request. So, I'm wondering, what should I do if I meet her again next week?

EDIT:

"I sent her a message on Instagram, but she still hasn't replied, and the number of followers and following remains the same. and this week I waited in the same place for 45 minutes hoping to meet her, but unfortunately, I couldn't find her. So, back to normal life. Thank you, guys, for all the advice."