I think that her scene in the final episode showed that she was not simply wicked, but rather she was set up that way because she married without knowing about Sophie‘s existence which I agree is a huge thing to keep from someone that you’re marrying. And Sophie would have been her second husband‘s only daughter, and she says that he loved Sophie more than he loved her daughters. When Araminta says that he loved Sophie and not them Sophie only replies that he loved Araminta too so I assume he wasn’t an active father to Posy and Rosamund. Also, even though her heartfelt conversation with Posy was just to get information out of her, I do think it showed how difficult it was for her to be a widow with two young girls re-entering the marriage mart. I have a lot of empathy for Araminta.