Assuming she gave it away because she is “well off” is just not nice. The journalist I know was poorly paid for a stressful job - the internet has vastly changed the economics of the industry - in fact they lost their job because their is no money in it any more.
I would guess that the writer is a reciprocation type of person: that feels uncomfortable to be just given things. One lady I knew from the UK had it so ingrained that when given a slice of cake, she had to give us something in return. I also see the same thing a lot in New Zealand culture.
There is also a pride aspect. I literally cannot give money to my friends that could really do with it, even though $20 is disposable for me and is really not for them. Social obligation and status signalling make cash really difficult. Oddly enough people often accept gifts of my time and indirect costs, without reciprocation. For example I can spend time and petrol chopping firewood and they will accept the firewood for free, even though it would economically cost me far less to just buy some firewood for them however that would not be acceptable!
Edit: Also she is living in East London which is stereotyped to be relatively poor. The 2021 figures I could find were Waltham Forest (part of Walthamstow) average salary for female £31.6k/year, compared with £27.5k/year for workers in North East England (a poor part of the UK). London is way more expensive to live, so she is relatively worse off at a guess. My stereotype of female journalists is that they are doing it for their beliefs, not for the money (those that chase money go to the dark side).
From the author's bio and article, it appears she is involved in venture capital, angel investing, and gets surprise tax bills which amount to more than the average English person earns in a year. That's probably the kind of person who can part with $10k without much hand wringing. Having said that, I do think the author is commendable in giving it away, because for a ton of people just like her, I believe they would just take the money and do something much more selfish with it.
Does the author of the blog post being the GP of this post change anything I said?