Nilsmark turned professional in 1987 and competed on the LPGA and LET, winning on both tours. She  played in  5 Solheim Cup matches, sinking the winning putt in Europe's first victory over the United States. She captained 2003 (Europe's 1st win) & 2005 Solheim Cup for Europe and was captain of the 2007 European PING Junior Solheim Cup Team. After retiring from tournament golf in 2008, she came back at 52  years of age, playing two tournaments on the Swedish Golf Tour in 2019.

She lives in Danderyd, Sweden with her husband.