You must realize that the chimney removes lots of heat, smoke, sparks and some very dangerous gasses. If she is planning to open the wall to expose the bricks she needs to understand that doing anything to the chimney risks exposure to all of those items.

Once the wall is open, assuming it is closed up and the chimney is hiding. She needs to look carefully at the bricks or blocks, what ever is exposed for signs of soot or black streaks. If any thing even remotely looks like that call a chimney professional in fast. Soot stains are an indication that the interior liner has or is beginning to fail. The bricks or blocks that you see exposed is simply protection for the flue liner. If indeed there is one. Many older brick chimneys were not lined and the brick itself was the material exposed to the gasses and the smoke. Over time the bricks break down and can leak into the house. So if you have an unlined chimney, I would suggest again to get it professionally looked at before doing any restoration work on the exposed brick or risk a fire or exposure to fumes.

Once your sure that the interior of the chimney is intact and safe, the bricks again assuming that is what your trying to see exposed can be cleaned and touched up with mortar cement.