How to Naturally Stop Contacting a Senior

My senior has just graduated and is 20, while I am a high school senior—the most pitiful teenager right now. We went to the same middle school, but we weren't close at all; we just greeted each other occasionally. However, after graduating, we started communicating every day, with messages expressing regret that we didn't get closer and apologizing for not being able to look out for them more. Honestly, it feels overwhelming. I'm busy and attending winter school right now, so I can't check my messages often, but this senior has a reputation for being scary, so it's hard to cut them off all at once. I've tried to subtly break the flow several times and didn't even intend to just keep going, but they keep pressing me by asking what my reaction is. I even tried to ignore their messages without reading them, but since they are connected to all my acquaintances on Instagram, it's not like I can just cut them off completely. What should I do? They just asked me whether I'm applying through regular admission or early admission, and I feel like if I reply, they'll bring that up again. Since they have such a bad reputation, I'm scared.