Assuming her buddies did the same profiles and were fine, I’m guessing it was a combo of earlier nitrogen accumulation and/or physical stress such as dehydration, fatigue (hangover) etc.
Then again, it could have simply been that different people have different DCS tolerance, even on their best of days... i.e. with no fatigue, dehydration, hangover, or anything else.
If we knew exactly why one person gets hit and another doesn't, we'd be able to prevent it 100% of the time.