Marigold, Lily's mom, works as a psychologist at a day care center for the elderly, which can't be an easy job. She has to break up a lot of fights between senile people who think it's still the 1930s, as well as deal with their families, who aren't always the most likeable people. Still, her knowledge of human behavior makes her a really empathetic, caring person. Perhaps maybe even a little too caring.
To begin with, she worries too much about her kids. When it comes to Lonnie, she tries to hypothesize the best case scenario to explain his lack of focus and direction: "Perhaps he was […] simply a slow developer, one of those people who matured late, who […] found themselves and dazzled everyone" (3.5). On some level, however, she recognizes that Lonnie's situation isn't good. Her dream, for example, where she receives a package in the mail labeled "Fragile. Lonnie inside" (12.22), reveals her intense worry and fear for her son's future. The box, after all, is empty.
Marigold may be more optimistic about Lily's psychological state, but that doesn't mean she's still not concerned. Take the time she walks in on Lily reading articles about boys in Bestie. Marigold's radar for teenage development is so good that Lily immediately knows that her mom knows her secret:
Her mother stared straight into her daughter's eyes, and Lily suddenly felt that Mum knew all about her crush on Daniel Steadman. (19.39)
The fact that she laughs out loud when she discovers Lily with the magazine is enough to confirm that Marigold totally knows the score without Lily having to say a word.
Her kids aren't the only objective of Marigold's ongoing psychoanalysis, though. She also has a tendency to get a little too close to some of the elderly clients at the day care, whom Lily has nicknamed "lame ducks" (3.37). Marigold keeps bringing them home and caring for them when their families go away, which is usually disastrous—one dude actually stole Lily's pants.
Marigold finally promises Lily that she'll stop doing this, but this doesn't keep her from feeling guilty that she can't help Mrs. Nightingale's daughter-in-law, who desperately wants a second honeymoon. And, of course, ultimately Marigold caves to her feelings of guilt. And while she clearly loves her kids, this means she prioritizes her work life over her home life since Lily has explicitly asked her mom not to bring clients home any more.
In the end, Lily's not kidding at the beginning of the book when she calls Marigold a "softie" (1.7). She cares intensely for others, and while her devotion to her career could be read as selfishness on her part, she's also doing it to provide for Lily, and for Lonnie, if he needs some help. Remember: She's a single mom. Plus, she's a lot like her own mom—always seeing the best in people and wanting to bring it out. Perhaps this is part of why Lily always assumes the worst. Someone has to balance Marigold's optimism, after all.