The lines that descibe the monotony are the following ones:
1.No time hath she to sport and play:(she can't do anything else)
3.She weaveth steadily,Therefore no other care hath she,-she is weaving all the time and does not think about anything else
4.She lives with little joy or fear-she doesn't experience the emotions
5.The sheep bell tinkles in her ear- I think this one also describes the monotony: it compares her monotonous life to that of a sheep