Slide it carefully out of the pot and take a look /feel around the roots. You will know straight away if they are:
(a) Underwatered, because it IS a possibilty! You should feel some moisture a round those roots and they should not be over warm. if its very dry around the roots its asking for a drink!
(b) Overwatered, saturation around the roots. Both ways CAN cause a plant to droop like that! If saturated, add a couiple of inches layer of clean dry soil to the bottom of the pot and put it back, the roots will quickly find refuge in the drier soil and recover. Let it dry out well.
I can't see it being anything other than one of the above 2 reasons. Its not lack of light, that does not happen. Its nothing to do with lack of nutes so dont be tempted to go that route, the leaves are green and healthy. Possibly the high temps could affect it, try to get a fan running through it and rememeber she will need to drink more water.
Check your roots and let us know?