Lack of ascorbic acid (vitamin c) is the most probable cause of bruising. It's primary function is in collagen synthesis and vascular homeostasis.
Lack of tocopherol (vitamin E) works in tandem with vitamin C to repair tissue; however this is rarely the sole cause of bruising.
Lack of vitamin K is the most common cause of external and internal bleeding. Sources of vitamin K include those produced by our intestinal flora (menaquinone, menatetrenone) and dietary intake (phylloquinone), which is commonly found in green leafy vegetables. However, low vitamin K is rarely caused by the lack of bacterial production or dietary intake. Rather, it's usually seen in individual suffering from hepatic (liver) conditions such as hepatitis, hepatic obstruction, trauma, or medications (warfarin/coumadin).
Zinc "helps" in maintaining healthy connective tissues.
I may suggest though that your wife consult with a physician to rule out any type of developing, hereditary, coagulation disorders (ie haemophilia, coagulation factor deficiencies, platelet aggregation disorders). I hope this answers your question and her issue resolves.
NOTE: Lack of iron (anemia) does NOT cause bruising. Normally during blood loss (ie menstruation, GI bleeding), a person may become anemic and coagulation factors are depleted, which in turn may cause bruising.
I'm a Clinical Laboratory Scientist and am familiar with vitamins and disease states; I'm a firm believer in alternative and homeopathic medicine.