I dare say it’s hard for a 9 year old not to compare her lot with the friends she sees all the time. I do have some sympathy, since my folks were always apparently worse off than those of most of my school friends - nice new clothes instead of a few hand me downs, riding lessons, ballet lessons, etc. were some of the things I longed for but didn’t even ask for, because I was well aware from a very young age of just how tight money was.
You can only try to show her how comparatively lucky she is compared to so many in the world, not to mention in the U.K., who’d consider any bedroom of their own, however small, plus of course running hot water and heating, to be a luxury.
Maybe she will need to be older, but I’m sure the penny will eventually drop.
Our dds had friends with bigger houses, some with swimming pools and apparently endless expensive new clothes, etc., but we were comfortable enough and I don’t think they ever felt poor.
However IMO it only truly dawned on them how comparatively lucky they were when we took them on a safari holiday to Kenya (yes, I know how that sounds, it was a comparative cheapie 3 rather than 5 job) when they were maybe 15 and 18.
Almost everywhere the safari vehicle stopped, children were surrounding it, clamouring for pens.
At one point I bought a whole box of Bics, in order to have enough to dish out.
Dds truly marvelled at how happy the kids were, just to get a pen. It was the first time IMO that the penny really dropped.
One dd eventually went on to work for an aid organisation, and has worked in that sector for some 20 years now.