It is, I'd say. A miniskirt does not have the same apparent intention as an ankle-length skirt.  Perhaps they are trying to bend the rules so they still feel "attractive" with all the attention they recieve from men?

Well, without knowing the woman or her church, I can't answer that question fairly. I can only speculate. However, I would say it is likely that the woman thought it was okay, since it was still a skirt and therefore within the rule espoused by the church. I doubt that the church said "Wear a skirt with a high center front slit."