...

she was born from a maid

Because she is a "disgrace". He claims that the maid pushed him into sleeping with her when he was drunk and threatened him once she got preggy. All high society knows this story.

It's a disgrace for a married noble man to have a child from a maid, so he pushed all the responsabily into his daughter and she was the one who received the mockery from everyone including her family.

I see. Thanks!