What does a girl call the second husband of her widowed stepmother? [closed]

A step-parent is a non-biological parent married to a biological parent. For this reason, if a stepmother's husband, being the natural father of children, dies, and his widow remarries, her later husband(s) are not step-relations to her stepchildren. Such a husband is the 'stepmother's husband'. Legally, and conventionally, that's all.

This does not mean that a child or children cannot call the husband 'Dad', 'Uncle', etc, if they wish.

Step-parent

a parent who is married to the father or mother of a child, but who is not that child's own father or mother.

Step-parent (Cambridge Dictionary)