Is a second (real) apology needed if the 1st one wasn't sincere?

Once in a while, I think about it and it's like a debate between apologizing again (for real) or forget about it because I did followed through with actions along the way.

We've been friends for nearly 2 years by now. Both of us just turned 18 not so long ago and have come a long way. Originally my plan was to use her to get better grades at math and chemistry. I didn't mean anything in that first apology a long while back. It's afterwards as I got to know her better that things changed.

She helped me and did nice things when I didn't deserve it. So yeah I was wondering if at some point I should apologize again, for real or not?

Is a second (real) apology needed if the 1st one wasn't sincere?
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