I'm actually not sure when this trait of Dora came about. Liked they say, learning should always starts from home so most of the time, I will try my best to speak to her in Mandarin but guess our helper also aids her English understanding as well. Strange thing is, she speaks to our helper in Mandarin and this has caused many funny situations at home.
Keep it that way lil girl. I hope you will find passion in learning Mandarin just like me!