Save the scolding and punishment. Get a one-piece snap-up or zipper-up sleeper (like this: http://www.llbean.com/cd-1/37901.shtml), cut the feet out of it if there are feet, and put it on her backwards. This stopped my son from being able to take his clothes off and therefore, he couldn't make a mess.
Also, I would appeal to her obvious desire for tactile stimulation by putting together a sensory table--put it in the back garden and put play-doh in there, let her play with cornstarch and water, let her play with mud and wet sand, rice, water, anything squishy. Give her ways to satisfy that desire in appropriate and acceptable ways.
All the best to you and your family.
Oh I feel your pain :( my daughter is 26 months and does the exact same thing. I have no idea what to do either... nothing works - I've tried restricting her access to her nappy but she still gets into it, I've tried getting mad, staying calm, having her help me clean, banishing her to the bathtub until I'm done cleaning and can deal with her..... she will cry and apologise, then do the same thing the next day. I'm over it.
If you work out the answer, fill me in!
PS: I've been told it's a sign of high intelligence. Not much consolation.