Reaching out to ex-friend to congratulate them?

I had a pretty large friendship breakup with a girl my junior year of college around 3 years ago. Looking back I regret the way it ended and never wanted bad blood with her. We haven’t spoken in years but I just recently saw a linked in post about her getting into her dream grad program.

Knowing how hard she worked for that, as we went to undergrad together, I have the urge to reach out and congratulate her (and also tell her that I’m sorry for the way things ended) but I don’t know if it’s a good idea.I have no expectations of her to respond, but it just feels weird leaving things as we did and not being able to congratulate her when she made such a huge accomplishment.