Tania's actions...Spoilers
I found her to be terrible, She was falling for someone while her husband was in a concentration camp. She hardly ever spoke of him. I don't see how she could be falling for someone when she must know what he is being put through. Yes everyone has desires but hers went overboard. She wanted to get married to her husband sister on top of her betraying her own husband. I get we want what we want but she had very little family and moral respect. She really did not want Hannah to return.
She may have even knew why she gave herself up the look Hannah gave her seemed to me to say everything. The husband was eying her even at his own wedding. They both were bad.
It was also strange how quick they came together. Just another clue they had no respect for the spouses.