What makes two people get on? When we meet someone, we quickly form an idea of their intent. I took a coach on Boxing Day from London to York to meet the woman who became my mother-in-law. It took eight hours, which made me late for dinner, but showed commitment, at least.

The main course went well. The rest of us were in the dining room when the pudding bowl exploded in the microwave, presenting her with a dilemma. She picked out the large bits, she told us later, and served it anyway. Inevitably, a shard found its way into my bowl and I had to say so. "Oh dear," she replied, as she took it away. "I suppose you're going to think I'm trying to kill you, now." She went off for ice-cream. Which sounds, of course, like a set-up for the familiar mother/daughter-in-law dynamic of antagonism, competition and one-upmanship. In fact, I share it for the opposite reason, as it introduced me to some of her best qualities: her pragmatism, her anarchic sense of humour and her complete lack of apology.

To be friends with a person, you probably have to share some attributes. We laugh together at all sorts of things, some of them a bit inappropriate, which alone may be enough. But the most interesting people in your life are those you learn from, and this tends to arise from difference.

I am not pragmatic or practical. I find life's twists surprising and alarming. My mother-in-law, like the line in the Rudyard Kipling poem, meets triumph and disaster alike. With a cup of too-strong tea and a bun, if she is present, or a prompt and pithy card, if not. I can feel hard done-by, that life is unfair, but she seems to place few demands on the universe and has no sense of entitlement. She takes it as it comes. I admire that evenness and stoicism.

It helps, I think, that we rarely talk about her son. She is a private person and acknowledges our privacy, in turn. There are unspoken boundaries and we both observe them. This was a lesson to me in itself; that in relationships, you don't have to say everything, all the time. I am much more self-sufficient now, and you need this, as a writer.

That said, when she speaks, she does so unflinchingly. Having someone write a novel in the family is hard. People tend to scatter. She was the only one to offer to read a draft, did so twice and gave honest, detailed, written feedback. This is priceless. She also tells you when she hates your Christmas gift.

I wondered if her children would recognise this account, or my parents this version of me. Maybe not. At its best, I think becoming an in-law can be a chance to be the daughter you wish you were. Calm, kind and patient. Someone who hears without judgement or taking it all personally. There is something very cathartic in it.

Above all, though, I find my mother-in-law to be capable. There are times when you need a friend to listen, and others, when someone who can prepare two full meals in ten minutes from week-old groceries, does the trick. The latter, I find, is much harder to come by.

In My House by Alex Hourston is out now, published by Faber & Faber and available from Amazon.