There is another IGI [ex local reg] entry for exactly the same date 1669-06-22 BUT it gives the child's name as Issable Harrison, probably the illegitimate d/o Issable Harrison & William Taggart. As Frances notes, the IGI has a tendency to "legitimise" children in this way. If the child was the eventual wife of William [3] Taggart then this might explain why Joyce Oates named her as "Taggart". This raises the question - who was this other Wm Taggart and what relationship did he bear to Issable's eventual husband? [and hence her own relationship to her husband] - more answers beget more questions!
Rgds JohnL