Can a Muslim divorcee (who was Hindu before marrying a Muslim) converts back to Hindu after divorce?
Well it entirely depends on which country you are in. Please be careful while converting back to Hinduism leaving Islam, because in some countries who will charged to death for abandoning Islam. But, mostly in non Islamic countries, this doesn't apply anyways. This wiki article of 'Apostasy in Islam' gives a fair picture as to in which countries execution is the prescribed punishment for apostasy.
Next, lies, "Can a Muslim divorcee ...???" At first place, in Islam, there is distinction between Muslim and Mumin (believer). So, I guess, you're talking about a Muslim only. Then there wouldn't be any problem for a Muslim who wasn't a Mumin at first place to abandon his religion. But if one was a perfect Mumin, he/she wouldn't even think of this question.
May the creator guide us all.