Is Diprosone really effective?

Hello to all, I would like to have your opinion on this medication please. My sister has currently been prescribed Diprosone http://www.drugdelivery.ca/s3446-s-DIPROSONE.aspx because of a skin disorder, her skin is causing a flat, itchy, violet rash on the wrists. My mum took her to the dermatologist and he told her to use this medication. I went on the net to have some more information on the type of medication it is and how it works and it seems that:

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This medicine contains the active ingredient betamethasone dipropionate, which is a type of medicine called a corticosteroid. Corticosteroids are medicines used for reducing inflammation. Inflammation of the skin happens due to irritation of the skin, and is caused by the release of various substances that are important in the immune system. These substances cause blood vessels to widen, resulting in the irritated area becoming red, swollen, itchy and painful. When betamethasone is applied to the skin it works by acting inside the skin cells to decrease the release of these inflammatory substances

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It is also use as:
• An eruption of hard nodules in the skin accompanied by intense itching (prurigo nodularis)
• Area of thickened itchy skin caused by rubbing and scratching (lichen simplex)
• Eczema
• Inflammation of the skin
• Inflammatory skin disease known as discoid lupus erythematosus (DLE)
• Psoriasis
• Severe, widespread reddening of the skin (erythroderma)
• Skin disorder

I would like to know if it is eventually a very effective medication?