Sometimes you have to accept that you made a mistake and it's time to move on. If she's happy in her life right now, don't dig up old wounds. Like that song says, 'only miss the sun when it starts to snow, only know you love her when you let her go, and you let her go'. You might not love her but you let her go, it'll be a regret for you but maybe it's time to move on.
Why do you guys do this "not ready for a relationship so lets break up so I dont hurt you" because that still hurts us.😭 Anyway, just to give you some inaight to how she might be feeling... it depends on how the relationship went and the break up, she will either have closure and decide it wasn't the right thing for her in which case it is unlikely you will get her back. Or she still has feelings for you but she feels like you let her down or basically flaked and she wants to avoid a repeat of going through that again. I'd suggest inviting her out for a coffee or drink and talking to her about how you made a mistake, that you'd like to try again but you realise you are going to have to earn her trust again but you'd just like her to let you have an opportunity to do that and prove to her that your reliable/dependable. Don't expect her to welcome you back with open arms (she might or maybe not) and dont expect an answer from her. Then just keep asking her out and doing things that show you care, that you want her, and that she can count on you. One other thing that might be useful to keep in mind - I once heard an analogy that love is like a bank account, you start with a zero balance and each positive interaction you have puts miney into the bank and each negative withdraws money. If you have a negative balance for too long eventually your account will close and you are unable to open a new one. What a lot of guys who have a big negative balance dont realise is that the slate doesn't get wiped clean just by sitting down and saying you want to try again. My ex, for example, got pissed off because after years of berating me he decided he didn't want to lose me so lets just turn over a new leaf, start again. He got angry and gave up when I didn't do the same but I couldnt just reset the balance to zero as I was so hurt, angry, and mistrusting.