D错。
Being a few minutes late指的是人，跟后面的reason不对称。另外你说的对，Being..可以做动名词，但是指代要清晰.如果要选D,正确地说法是: Being a few minutes late，she should not be dismissed.
(就像你在朗文上看到的例子:Being a quiet sort of person, I didn't want to get involved.一样)
选C是因为 The fact(that...)与reason匹配.
在英语语法里，句子的对称性很重要，尤其在GMAT考试中能体现出来.
希望可以帮到你 谢谢