honestly, as the story progresses, you can tell she really loves her daughters to no end. I feel like the author/artist wanted to emphasise how plain/possibly unattractive they looked to others and they had the mom be practical and aware of that in the context of the society they're in and what their prospects for marriage would be like.
You clearly haven't read this story properly/maybe just stop before you understand her.
She is not saying her girls are ugly, but she is looking at them objectively. You cannot deny that there are people who are effortlessly stunning, that them simply being there is enough to make them the center of attention. Mildred (the mom), the baron, and ashley were the examples of those people. Whereas, there are people that are more "plain" and needs more effort to show themselves off to gain people's attention. These are the sisters, her daughter. Hence why she said its "unfair".
The mother just handled and viewed things realistically because she understood other people's views and wants the best for her daughters. She thinks that her daughter must get the best men to be their future suitors. That's why she tried her best to taught them manners, how to walk and how to behave themsleves, also how to dress themselves.
Modern "everyone is beautiful!!" Is not what was needed for them to live well in this era. And come on, be truthfull, even in modern world, appearance matters.
The point is not how she looks in your eyes, but what she looks like IN THE STORY. She is told and described as BEAUTIFUL. If you say she is plain, it may be because if the art of the artist, or maybe the design is not up to your taste. But the point of the STORY if you actually read the 9 chapter u said, she is told to be BEAUTIFUL.
YES her daughter look normal and as this story progress, thanks to the mother having ideas on their dresses and her education of etiquette and attitude for the girls, they are highly praised and they are seen as beautiful too.
I agree with the comment above me, she's a10 mother and I would love to have someline like her as my second mother or maybe a friend. She looks very fun to be with.
I don't like the stepmom already her daughters aren't ugly at all. I guess since their noses are a tiny bit bigger than hers they're monsters.