I read a lot about them in the old DWW forums and also in several emails with company bosses.
The rivalry between the two was real, it was not fake and the company took advantage of it by making them fight and wrestling in different ways and styles.
Nicole barely won two of those fights and Ingrid won all the others and she humiliated Nicole in all of them, such as in her mud fight, or in her prostitute fight, Mother of All Catfights. Some fans told me that Nicole was so beaten and exhausted after those last two fights that she couldn't even get up.
The brawls between them were famous in the company, especially one during a fight on mats, aftera lot of surrenders, Nicole refused to give up and that got out of hand because Ingrid refused to let go of her and kept her trapped without letting go.
I saw all her matchs and they was really wondefull, despite of course I had my favorite betwen the two.