There’s a painting, early on in the Berthe Morisot show, that looks like a snapshot. The kind of photograph you take of your friends, the kind that you shoot on film, when nobody can look back at it and pull a slider through a split-second of captured time to find the most flattering expression, or delete because somebody has been caught off-guard. Summer’s Day is a scene taken in the midst of things - its two women have just boarded a row boat, they are pushing off from the side of the water. One looks away, the other we see directly, her face the natural glance of someone just about to say something.

I’ve always found it hard to cut through the saccharine fuzz of Impressionism - the washy pastels, the rosy cheeks, the frills and hats - but Morisot’s paintings offer an edge. Her work is arresting, I found her portraits demanding my attention, as alluring as the promise of teeth beneath gum.

The show is on at Dulwich Picture Gallery, the first UK exhibition dedicated to Morisot - a painter who fought her own among the big boys of Impressionism in the late 19th century, but has failed to maintain their reputation since - since 1950. It’s a funny little thing, so keen to stress the influences of older male artists on Morisot’s work, complete with side-by-side comparisons of paintings by them, that hers is almost drowned out. A third of the paintings on show are by men who are not Morisot.

Still, the women she painted are the most interesting works on the walls, persistently tugging for attention. The arched brow of Girl on a Divan; the ghostly hand and thoughtful profile of Paule Gobillard Painting; the unobserved quietude of her sister, house dress given the gravitas of a ball gown, watering a plant; the furrowed brow and fist, raised in determination, of her seven-year-old daughter in Children with a Basin, so pleasingly vivid in comparison to Impressionism’s usual cherubic portrayals of little girls.

Morisot painted her daughter - Julie, her only child, born when she was 37 - a lot. The final painting of the show is its most entrancing, and most poignant: the girl as a teenager, desultory and pink-eyed, dressed in black for the father who died the year before. She could be an adolescent in a bedroom in the 1970s, which her middle parting and blouson sleeves recall. Crucially, Morisot also painted around her daughter. I was more interested in the caption accompanying The Fable than the painting itself, which shows a little girl standing and talking to a woman who is sitting on a bench, in a garden: “Morisot frequently depicted her daughter being cared for by others, their work allowing her to pursue hers.” She exhibited alongside Cezanne, Degas, Monet and Renoir in all of the Impressionist summer exhibitions - bar one: that which followed after Julie’s birth.

It’s there if you think about it: if Morisot is painting her daughter, someone else must be looking after her. Painting takes time and attention. It is work, the same way motherhood is. These paintings are as much a portrayal of girlhood as motherhood, of the fierce determination to create in more than one way. I wonder if this was her intention; as much to capture the bewilderment of raising a child as to define herself alongside it.

For the past few weeks I have spent Monday afternoons writing. I pay a younger woman - more energetic, more qualified in early years care than me - to watch the baby for four hours. I pump milk and sterilise bottles and put them in the fridge. I lay out toys and make sure he has napped well before she arrives. Then I put my phone on loud in case she needs something and put it, face down, in the corner of the studio. I sit at this desk and I try to think about words, instead.

I savour these afternoons and I dread them. For the first time in months I can access the deep concentration that arrives with a stretch of uninterrupted time. I put words on a screen and each one gnaws away at the sense that I have lost the thing that helps me to feel alive. Sometimes the baby cries and I clock the time, watch the minutes rack up before I stand up and go to him. Sometimes it feels like work, sometimes it feels like freedom, often it feels like both.

I’ve often questioned my writing about motherhood. My loudest inner monologue is a negative one, and it tells me that nobody cares, that this is of an intimacy that is boring to everyone else. Still, I persist. It bubbles up like the strange pains that occupy different parts of my body for a few days then fritter away. Kinder friends tell me I am writing to preserve an extraordinary time. Rhiannon Lucy Cosslett write about this recently (I have relished her column since before I was pregnant): “It is only after months of doing this that I have understood how little of early parenthood is written in real time, for understandable reasons. But to reconstruct it in retrospect is to always lose something in the recounting.”

Summer’s Day was painted during Morisot’s matrescence; Julie had been born the previous November. An upper-middle class woman, Morisot employed a nurse for Julie, and the two would walk in the Bois de Boulogne with the baby. She wanted to paint, but she didn’t want to leave the baby, so she brought models to the park, made them sit in a boat. The nanny sat with Julie nearby. The illusion of spontaneity, of a moment, a splash of light, caught in time, is key to Impressionism. But perhaps that’s contributing to the urgency in Summer’s Day - a new mother’s haste to balance her art with the invisible tether to her child, gurgling a few metres away on the riverside.

The exhibition claimed Morisot “was one of few women who successfully combined art, marriage and motherhood”, unlike her sister Edna, similarly trained, similarly respected, until she “gave up art to focus on her roles as wife and mother”. How glib, how short, how unsatisfactory I found this little caption. Did she ever, I wonder, feel she was doing it successfully. Did she feel she had to grasp for time while other women looked after her child, did she feel she should have been mothering rather than painting her motherhood, did she argue with her husband when it felt impossible to do it all?

The show made much of the femininity of Morisot’s work, her use of colour, the way her male contemporaries saw her, while endlessly sandwiching her paintings between those made by men.

But to me, the femininity in her work emerges from her capturing the innate complexities of womanhood - to stand before a mirror, in tulle, not knowing if it feels right; to offer a subversive glance above the trappings of your class and corsetry; to look into a cradle with as much fear as love.