As far as I am aware Larrissa Tudor was neither a liar or attention seeker, indeed all her actions indicated the complete opposite. She made no claims during her lifetime and all the speculation as to her identity came about after her death.
I agree totally with you! Not only that she didn't make any claim but even her husband didn't make any claim in her name after Larissa's death, as I see he never wanted to speak about his wife or her identity after she died. I see that they wished to go unnoticed. The claim appeared really recently -long time after Larissa's death- (early 1990's) thanks to Occleshaw and his really imaginative book. :-/
I've always wondered why about this hermetic attitude of her husband, -I repeat, I don't believe she was Tatiana- but this makes the story even more mysterious, as well as that the little information that we know about her doesn't match (like birth date).