You can read the character sketch of Martha Washington here:

Helen didn't remember what happened to her during first months after her illness. she started identifying objects through hands. After her sickness, she started using crude signs to communicate with others. she was a naughty child.Helen became friend with a little coloured girl Martha Washington, the daughter of her cook. Martha understood Helen's signs without difficulty. Helen always pressurizes her and made her made her do what she wanted to do. Both together spend a lot of time in kitchen, kneading dough balls , making ice cream, grinding coffee, quarreling over the cake bowl and feeding hens and turkeys. They also hunt for the eggs in the long grass. The sheds where the corn was stored , the stable where the horse were kept, and the yard where the cows were milked morning and evening were unfailing sources of interest to Martha. In fact she was a mischievous girl who submitted to Helen's mischief most of the time.

As its too lengthy to type out here.....I suggest you to read from the character sketch part of Helen Keller "the story of my life" which is available in this app....you can easily refer from it. The charactersketch given here is not very long so for more points google it.