Contrary to long held beliefs and taboos, 1st Cousins CAN have Children together without great risk. Scientists today say there is NO biological reason to discourage Cousins from marrying. Your Parents and Her Parents approval are an entirely different consideration. If this is unacceptable to them it will definitely impact Your lives - and probably that of Your Children
In the US, it is generally not legal to marry a close blood relative. I understand that this is more common and accepted in some countries, so I am going to assume that marrying your father's brother's daughter is acceptable where you live.
The issue is with having children. Having children with a close blood relative increases the chances of having a child with significant genetic abnormalities or other medical conditions. Blood type isn't the problem in your case - it is a problem of re-combining genetics. A gynecologist isn't likely to be the best professional to consult. If I were you, I would seek out a doctor who specializes in genetic counseling before you proceed. You can then understand the risks and make a decision.
Good luck to you, whatever you choose.