Actually there is at least one adult at my home for most of the time, just because I had to work late on that day and therefore only my helper was at home with my girl after my mum left my home. I also understand that my helper needs to take care of bb and do houseworks, and since my mum or my hubby are usually at home, I'm never too demanding on her in taking care bb or playing with bb.
What made me so angry was that she spent at least 30 mins in kitchen to prepare dinner for herself, and did not switch on dvd for my girl to watch or gave her some toys/ books while she was busy. When I asked her to keep an eye on bb, she talked to me very loudly and was very rude. My feeling is that she doesn't know how to take care of a yound child and doesn't have such 'heart' to do so, that's why I let her go.