She was a material witness ?. I would suggest that is stretching a point. She was witness to a child crying on another night. It is a big leap to make that material to an alleged kidnapping that took place at a different time.
Her evidence seems to have been given more credit than it possibly deserves. As you say it wasn't relevant to the night of the disappearance.
Her evidence and that of Yvonne Martin seem to be grouped together and given a status of their own, possibly because they both point to neglect by the parents.
Yvonne's statistic that "99.99% of missing children is due to the parents" (I could get the exact words) is way off the actual recorded statistics. (99.99% implies only 1 case in 10 thousand would be stranger or friends involved. That is absolutely untrue.)
Pamela's child crying for 75 minutes shows they were possibly skipping checks.
Both witnesses point to the parents but both apparently unreliable.