Why was my greatgrandmother able to have a normal child at 47 and I can't get pregnant at 41:/?

Depends. Each body is different. Even you two are related the differences betwenn the way your body works can be large enough to cause this fact. If you tried to conceive for more than 1 year without results, go see an ob/gyn to start with.
Fertility variables. Your great grandmother by definition had a different genetic makeup that you and a different spouse. She obviously continued to be fertile until 46/47. Your differing genetic makeup & all the various factors that influence fertility (including your spouse) hamper you. An evaluation by a fertility specialist can give you an idea if you can be helped if you desire.