Ok so this may go on for a bit but I want to give the full context to my situation.
During my first year of university I was in a really bad headspace (sought and got help so that's mostly in the past) but while I was in this panicked state of mind I wanted a sense of familiarity since I had no friends a the time at uni nor many outside. In an aim to achieve this I messaged a girl I was/still am romantically interested in however I want to stress that despite my interest in her romantically I reached out just on the basis of being friends, she rejected me in high school and I want to respect that she has no interest in me at this current time like that.
Anyway so I started by sending a simple "Hey there" message wanting to chat. Immediately I came over with this sense of panic and regret and deleted the message. Then I did the same the next day and the cycle repeats for about a week. As you can probably gather I was not in a great place. Now cut to the next week and I get a notification of a response. I'm panicking and I haven't even opened it yet and that's when I realized what had happened. The message I received was just politely asking me to leave her alone and that we aren't friends. Then I realized that all the messages I had sent were only ever deleted on my end and for her she got EVERY SINGLE ONE. I felt terrible and desperately wanted to apologise properly but she had already blocked me by the time I figured out what to say. A completely understandable reaction on her part as from her POV I was essentially constantly messaging her unprovoked.
I've been feeling terrible ever since. I really care for her and would absolutely value a friendship between the two of us even if it never went any further than chatting online a few times or hanging out once in a blue moon. But at this point I just want to have a chance to apologise properly and explain myself. Despite blocking me on their main account I could still message them on their other account but I didn't want to breach the boundaries that she had made between us. However, it's been over a year at this point and I'm just feeling worse and worse about it. I want to apologise... I want to be friends but I just don't know what to do. Is it even possible to fix this? I'm in constant anxiety and confusion about it and now it's affecting my daily life in ways like lack of sleep/very bad schedule, spurts of panic and lack of appetite. I'm just honestly not sure what to do from here.
Sorry for the very long post I just wanted to get this out there

Any help/advice/anything would be greatly appreciated