Not only that, but if Jack was the “working class, coarse Essex accent” kind of person she claims to be, she wouldn’t be Mama. Working class Essex people don’t use “Mama”. You’d have the piss ripped out of you for having ideas above your station.
If it had been true from the outset, I could go with it - because one of my offspring's first word, much to my eternal smugness, was 'Mama?' (the other one's was, like mine back in the Dark Ages, 'Tat' - meaning Cat). I had never used the word, she was in a home where I was called Mummy, but she called me Mama and I went with it - by Secondary School, it had changed to Mumma, mummmummummumma and Muuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuma, but that all started from her first summoning of me for attention. I got stick for it from the ex, as he thought it was trying to be posh when I was underclass scum, but nobody else ever said anything about it - to my face, at least.
Hers didn't do it at first - only after being around somebody else who did. So clearly chosen for either show or because it became an internet thing. Or he doesn't really do it, he calls her Mum like most kids in the London and Southeast do and she just wanks it up for the internet.