Prajnaparamita, mother of all buddhas, may have one head and two or four hands, she can be standing or seated. The above has Nepalese-style facial features, hair ornament and lotus base. She holds a rosary and a pot of water (an unusual attribute for this deity) in her upper hands. Her lower right hand displays the gesture of supreme generosity, the other once held the (broken) stem of a lotus that supports a manuscript (the Prajnaparamita sutra).
This is a good example of how tricky it can be to identify a deity. There is a one head and four-armed form of Manjushri but he would hold a bow and an arrow as well as a book and a blue lotus.
On the Himalayan Art Resources website this figure is labelled Prajnaparamita, and indeed the four-arm form of this deity would have a rosary (missing here) in her top right hand and manuscript in the other. The lower left hand is held flat, as if to hold a bowl, the other holds an object which should be a vajra sceptre although it looks different.
This other West Tibetan image depicts her with the same hand position and attributes, including the unusual object/vajra in her lower right hand.
When seated she is usually framed by lotuses, one of them supporting the manuscript.