I ran into something similar just this morning. A user had effective rights to delete, volume rights to delete, and feature rights to delete both inherited and directly applied to her account. But trying to delete returned a Permission Denied error. 

In our case, her AD group was also imported into laserfiche and did not have the "delete" feature right, which silently overwrote her explicit permission. Check up and down all her groups, make sure her groups aren't part of groups which have deny permissions (both AD and LF groups). And if her AD group doesn't have a feature right, apparently that will overwrite the user's feature right.