Fari baba ja is her version of get lost or get out. Not just Di, anyone who scolds her or tells her not to do something she says baba ja.
Once she held Chotis hand very tenderly and took her to the door and then shouted baba ja! Must be annoyed at Choti for some reason.
In Iran, while we were going some place by bus, Choti was sitting besides Di and Azra was on Di's lap. Suddenly what got over her she forced Choti to get up. So Choti bribed her with a chocolate. Azra let Choti sit besides Di and her till the chocolate lasted. Once she had eaten she was back to baba jaaa... Ek dum shaani hain Azrajaan