What are the benefits of vitamin B12 in females?

I think you are more interested about the results of the deficiency, right?

B12 deficiency:

Vitamin B12 deficiency can potentially cause severe and irreversible damage, especially to the brain and nervous system. At levels only slightly lower than normal, a range of symptoms such as fatigue, depression, and poor memory may be experienced.
Vitamin B12 deficiency can also cause symptoms of mania and psychosis.
http://en.wikipedia.org/wiki/Vitamin_B12#Deficiency

Symptoms of Vitamin B12 Deficiency
A deficiency of vitamin B12 can lead to vitamin B12 deficiency anemia. A mild deficiency may cause only mild, if any, symptoms. But if untreated, it may cause symptoms such as:
    Weakness, tiredness, or light-headedness  
    Rapid heartbeat and breathing
    Pale skin
    Sore tongue
    Easy bruising or bleeding, including bleeding gums
    Stomach upset and weight loss
    Diarrhea or constipation
If you think you have symptoms of vitamin B12 deficiency, you can ask your doctor for a blood test to check on that.
http://www.webmd.com/food-recipes/guide/vitamin-b12-deficiency-symptoms-causes


Are you by any chance a vegetarian or vegan? B12 is present to only to non-vegan foods like meat, eggs, milk, cheese, fish etc. Also, some companies started fortifying with B12 foods like cereals, but I don't know if that will be a good source of B12.
If you consume dairy/eggs then you shouldn't have any problem. For example, couple of glasses of milk are almost enough to cover the daily needs of B12. But if you are not consuming dairy, then I think that your best bet is to take supplements of vitamin B12, or to look more thoroughly about the fortified-with-B12 foods that are on the market.

On the other hand, if the deficiency is not the result of your diet, but the result of a disorder, then you must consult a doctor for some special treatment.

It's part of a disorder, genetically I have a hard time absorbing the vitamin from my colon, so I get vitamin B12 shots every other month. I have stopped for a year, and I think I might be feeling the effects.

Thank you

The top 5 health benefits of vitamin B 12 are:
It is needed to convert carbohydrates into glucose in the body, thus leading to energy production and a decrease in fatigue and lethargy in the body.
It helps in healthy regulation of the nervous system, reducing depression, stress, and brain shrinkage.
It helps maintain a healthy digestive system. Vitamin B12 also protects against heart disease by curbing and improving unhealthy cholesterol levels, protecting against stroke, and high blood pressure.
It is essential for healthy skin, hair, and nails. It helps in cell reproduction and constant renewal of the skin.
Vitamin B 12 helps protect against cancers including breast, colon, lung, and prostrate cancer.

Sources of Vitamin B12. Vitamin B12 is naturally found in animal products, including fish, meat, poultry, eggs, milk, and milk products. Vitamin B12 is generally not present in plant foods, but fortified breakfast cereals are a readily available source of vitamin B12 with high bioavailability for vegetarians