"A: Funny about my mother. All my life, from the time I was just a little kid, I thought of her as a sad person. I mean, the way some people are tall or fat or skinny. My father always seemed the stronger one. As if he was a bright color and she was a faded color. [...] But later, when I learned the truth about our lives, I found she was still sad. But strong, too. Not faded at all. It wasn't sadness so much as fear [...]" (26.1).
Louise Farmer, Adam's mother, is very, well, motherly. Although she becomes depressed after her family's relocation, she is still tender, comforting, and incredibly sentimental. Before she was lighthearted, always laughing at her husband's jokes and making Adam eat more to bulk him up. After the relocation, this freeness turned into nervousness. She watches Adam leave and waits for him to return, always anxious if he's even a minute late (10.16).
Louise surprises us a little by being somewhat rebellious against the Witness Re-Establishment Program. She speaks negatively about Mr. Grey and shows Adam some things from their past that she had boxed up in the cellar. Perhaps this is out of fear, but it reminds us – as Adam notes in the passage above – that she is strong.
Louise serves to show us what might become of Adam if nothing changes for him. Adam very quickly picks up his mother's fears of the Never Knows and her constant paranoia. If he were to grow up living a lie, hiding from the world, this is the life he could expect.
However, things do change. Over the course of the novel we find out that Louise was killed in a car accident. Well, maybe we shouldn't call it an "accident" since it seems pretty intentional.