THE FLT WAS THE FINAL LEG OF A FLT FROM WINCHESTER, VA THAT HAD BEEN DISCONTINUED THE DAY BEFORE DUE TO ADVERSE WEATHER CONDITIONS. TWO WEATHER BRIEFINGS WERE OBTAINED ON THE DAY OF THE ACCIDENT, BOTH OF WHICH INCLUDED THE STATEMENT THAT VFR FLIGHT WAS NOT RECOMMENDED FOR THE PROPOSED ROUTE OF FLIGHT ALONG INTERSTATE 48. THE PLT STATED TO A FRIEND THAT THE WEATHER LOOKED 'TERRIBLE' BUT WAS GOOD ENOUGH TO GET HOME, AND THAT SHE WOULD TURN AROUND IF POOR WEATHER WAS ENCOUNTERED. WITNESSES TRAVELING WEST ON ROUTE 48 SAY THE ACFT AT APRX 400 FT AS IT FLEW BELOW THE OVERCAST OBSCURING THE HILLTOPS. THE CEILING LOWERED IN THE VICINITY OF THE ACCIDENT SITE AND WITNESSES OBSVD THE ACFT IN A STEEP LEFT BANK 50 TO 60 FT ABOVE THE GRND. THE NOSE PITCHED SHARPLY DOWNWARD AND THE ACFT STRUCK AND CAME TO REST ON A HIGHWAY ACCESS RAMP. A FIRE ENSUED. FOG AND RAIN SUBSEQUENTLY ENVELOPED THE SITE PRECLUDING A MEDEVAC HELO LANDING ON SCENE. THE PLT SUCCUMBED TO INJURIES IN A HOSPITAL ABOUT 8 HRS AFTER THE ACCIDENT.