It may sound overly optimistic, but can you turn it into a chance to fix the problem for next time?
They’ve admitted they caused trouble for the others in the group, and were at least partially to blame, sometimes that’s the hardest part of confronting a coworker. If you can turn that into some areas they could work on, or steps to help the group as a whole, that seems to take the focus off of them screwing up and putting it on making sure it doesn’t happen again.
So maybe just go back to her some time when it would make sense and say something along the lines of “I was thinking about what you said and we all probably could have avoided the <bad consequences> if we had just <steps here>”...
Steps might be things like asking her to get her portion done early next time, or helping her define some milestones between start and finish that she should hit so it’ll be done as it should be (you didn’t mention if the work was late, just not done, or low quality).
No one wants to take extra steps and “babysit” their peers, but it’s usually so much easier than scrambling at the end and covering for them when it’s unexpected.