Haunted by the pain her daughter experienced before dying of AIDS, Valerie Emerson is trying to spare her son the same fate by refusing to let him have the medication doctors say will keep him alive. Emerson, 27, believes the three-drug cocktail that has subdued the AIDS virus in many patients will only hasten 4-year-old Nikolas' death rather than prolong his life. The state disagrees, and it asked a judge to decide who will get Nicholas: his mother or the state. Judge Douglas Clapp is expected to rule next week. Emerson, who is infected with HIV herself and has stopped taking medication as well, passed the virus on to Nikolas at birth. Nikolas' physician, Dr. Jean Benson, said the youngster had been thriving since he was taken off AZT in March 1997.