That's so judgemental how would you know that only27 That's just guess work . the girls father lives in another country and Christine says she hasn't had much involvement with his new family or seen him for two years, so the new partner probable doesn't really know the lass very well and as she's an adult daughter she probably doesn't even think of her as a child
I think it's incredibly sad that the dad hasn't kept up contact and involvement but that's not necessarily the new partners fault
If the granddaughter was seeing the family regularly, staying over like a lot of broken family arrangements having ,meals with them, playing or even baby sitting with her half siblings then of course the step mum would see her as part of the family and that would have been an unforgivable thing to do but if they barely know each other and she doesn't figure in their life (fathers fault entirely) then I doubt the new partner would even think beyond her own children