The question of restoration is a really interesting one, and the source of much back-room angst in museums and galleries. I am not qualified to do it, but I have studied it and would love to discuss the ins and outs.
But first, this news story.
It does not sound like this woman was in any way an official restorer. Nobody seems to have known she was doing a restoration, and indeed the local art preservation center had been making separate arrangements to restore the painting.
Also, judging from the images, she seems to not have had the skills to restore. I suspect this is the reason so many news outlets have picked up the story -- as normally they pay little attention to art unless it explodes -- and the reason for so much of the merriment in so many of the stories.
I also wonder how and when she did this. It is difficult to paint in public without attracting attention.
Normally a restoration job is a slow, painstaking process. The modern philosophy of restoration is to do as little as possible to the original image, to only touch the damaged areas and that as lightly as possible.
This, alas, was not always the attitude, and the reason for it today is so many thousands and thousands of artworks seriously damaged or changed by heavy-handed restoration in the past. And when I say the past, I am not talking centuries past either.
This case is further complicated by the fact that this is obviously not a fresco. Please bear with me, as this is going to get technical for a moment.
True fresco is the ancient art of painting with pure pigments and water -- not paint -- onto the wet plaster of a wall and letting the plaster and color dry together. The pigment bonds molecularly with the crystalline structure of the plaster, producing a permanent image that could almost be scrubbed with wire brushes and will last as long as the wall does, potentially for thousands of years.
The only drawback to this is that the color must be applied to fresh, wet plaster. This makes things go very slowly and carefully, and means that errors must be chiseled out and replaced. Also the results, although beautiful, are a little matte and lighter in color than rich oil paintings can be.
Michelangelo's Sistine Chapel ceiling is true fresco. It's why it is so brilliantly colored and clear even today.
But in order to save time, and to be able to use pigments that normally cannot be used in plaster because of chemical reactions, and to get the deep, rich effect of a "real" painting, there is also something called "fresco secco," or "dry fresco." It is not real fresco at all, just painting onto a wall. It's a mural.
The drawbacks to this are that the paint never really bonds to the wall's surface. Over time it flakes off, and restoration is far, far more difficult than with true fresco.
Leonardo's Last Supper is fresco secco. It's why it is such a faded, sad wreck.
Elias Garcia Martinez's Ecce Homo is clearly fresco secco, as can be seen both from the painting technique and from the flaking of the paint. It is a layer of paint that was applied to a dry wall.
This makes its restoration extra delicate. And the damage this woman did is going to be extremely difficult to undo, since what we have here is two layers of paint bonded to each other, over a wall.