Hands itch and turn red for about 2 hrs whenever she takes a shower, goes swimming, washes hands, etc. diagnosis?

Raynaud Phenomenon.: Raynaud's phenomenon is a condition resulting in a particular series of discolorations of the fingers and/or the toes after exposure to changes in temperature (cold or hot). See your doctor.

Allergy.: Possible reaction to soap or chlorine. Don't use soap on red hands. I believe it is a sensitivity . A good dermatologist will help.

Could be: Several things from as simple as dry skin to something more like cholinergic urticaria/aquagenic pruritus. in the meanwhile make sure you are good about using a moisturizer and consider your doctor, as the later conditions are related to your allergic cells being "hypersensitive".