She is standing up and, according to Wilkinson (all pictures below are from his work), that means she is the benevolent one ('positive'). Hippopotami standing on all four, though, are 'negative', eating and trampling down in the fields of man.

Taweret ('the Big One') usually is depicted leaning on a kind of support, probably signifying (I guess) her function of giving support and protection:

And then she has also some kind of connection with Ursa Major (Thigh of the Bull) according to the anciant Egyptians: