I think she found much more important duty "at home". I mean, sewing, helping her mother, take care of her health and of Alexej's, and have a look on what her siblings did. The IF was a closed family in a certain way, they preferrred the company of themselves better to anyone else's; maybe she found dull whatever was duty "out of home"; i think that, on the contrary, she very much preferrerd "duty at home". duty is always duty and, of course, we shouldn't steretypy a person, but i thinks is undeniable she was the one who best beared the wwight of duty in the family - along with Nicholas. In this side, she was justn like Nicholas, and NOT like Alix. Alix couldn't bear duty and formal duties mkore than a minute. On the contrary, Tat'jana possesed her father's self control & phisical resistence (and a stronger mental one, IMHO than N). That's way, IMHO, Alix needed her so much: Tatiana was as practical as she was and as much decisional but she was stronger and more resistant in everyday life.