Contrary to what Hitchens has said and written, she was no atheist and not a phony posing as a pious person, just a doubter whose faith was never firm.
DOES IT MATTER THAT SHE WAS A DOUBTER?
Not at all.
A person's deeds are what matter. Good deeds are more important than faith or piety alone:
And now abideth faith, hope, charity, these three; but the greatest of these [is] charity.Teresa was unquestionably charitable. That she continued a life of good deeds despite the fact she herself felt her faith was questionable is only greater testament to her goodness.
Goods deeds - even of doubters - are themselves filled with piety and FAITH.