That mark might stay for long and even may disappear, it takes time. It's because there is a puncture in the skin when the needle is inserted so the mark will appear sometimes for obvious reasons as a little blood might come out and a little other factors.
Well, I was advised in childhood and still advised to apply a cream called Thrombophob by Zydus company, it will be easily available in Ahmadabad. Apply her gently on her hand daily for some days. It is also advised that the cream is applied for next 1-2 days after transfusion so it keeps veins in good health.
And the most important thing, never go on transfusing only in one hand, make them rotate alternately. Once in left, next time in right, then again in left and next in right and so on so each vein will have adequate time to recover and come back to normal state and also that marks would be disappeared, don't worry.
![:)](http://www.thalassemiapatientsandfriends.com/Smileys/classic/smile8.gif)
-P.