Was my friend right?

He noticed how happy I am in my relationship. But how I just can't seem to let go of some things from my past relationship with my ex. His verdict is that I haven't 100% moved on, that there might be a tiny, 1% of things I'm holding on to.

I had her blocked everywhere, even on LinkedIn (lol). But on my graduation she sent me a congratulatory message on the fellowship group chat we're on, the only place she could reach me.

I simply responded "thanks!", nice and short.

Then.

Today's her birthday- my friend told me to be the bigger man, unblock her, and tell her happy birthday. Not to engage her in conversation, but just to tell her happy birthday. His opinion is that if I can't talk to/see her without feeling mad, that I haven't fully moved on.

So I did- I unblocked her, told her happy birthday. I was still a little annoyed while typing it. She replied just now, saying congrats on my graduation again, and, trying to start conversation asking if things are going well for me. I replied "thanks!" and ignored her questions about how things are going. And then just reacted with a thumbs up and kept it moving. I think that's the last bit of conversation I'm ever going to have with her.

Was I this okay to do?