Her pack
Try deleting it and reinstalling it first. If that does not work--here are some trouble shooting possibilities:
If you have more than one [default] replacement skin, it may be conflicting with Mira's pack. I would follow Carmen's advice on downloading the Mod Conflict Detector and seeing if that can tell you what it is conflicting with
before unnecessarily deleting all of your mods.
Ensure that you installed it correctly from the get go, and [if you did install it correctly] you may need to do the 50/50 method until the conflict can identified.