If the Murry twins form Meg's idea what healthy normality looks like, her mother is an example of impossible perfection:
Meg looked up at her mother, half in loving admiration, half in sullen resentment. It was not an advantage to have a mother who was a scientist and a beauty as well. Mrs. Murry's flaming red hair, creamy skin, and violet eyes with long dark lashes, seemed even more spectacular in comparison with Meg's outrageous plainness. (1.62)
Mrs. Murry defies the stereotype that smart girls can't be pretty, and vice versa. And that's not all that Meg envies: her mother also has a near-unflappable self-control, and a trust that Mr. Murry will return, that Meg wishes she could borrow. Her mother's role as the glue that holds the family together means that Meg is the more shaken when, through the power of the Happy Medium's crystal ball, she sees the pain hidden by that strength.
Mrs. Murry looked up from her letter, almost as though she were looking toward the children, and then her head drooped and she put it down on the paper, and sat there, huddled up, letting herself relax into an unhappiness that she never allowed her children to see. (6.48)
Mrs. Murry serves as an inspiration for Meg in more than one way: not only is she what Meg would like to be, but her suffering caused by her husband's absence strengthens Meg's resolve to do whatever it takes to fight the Black Thing and bring her father back home.