Well, you don't need to be a rocket scientist to realise that she is neither a good parent nor a cordial and affectionate person.
The thing about Grace (Ian´s Mom) is that we not only have Edwin´s impression that she is not a good parent and a really cold and distant person, we get this information from several independent sources throughout the story. We also can compare with other aloof characters. Hell, even Kath and Sophia are less distant than Grace! It says much when both the most sadist and the most eccentric character in the game are less cold and think higher of the MC than Grace ever did!Anaffective doesn't mean she doesn't care. In her way she is invested in her son future and wellbeing. We are speaking of motherly devotion, not motherly affection.
Read a bit between the lines. While for Kath and Sophia Edwin might currently be mostly a useful pawn, you can get closer to them and maybe more in later chapters. Grace considers Edwin scum and this is an opinion she had for many years. What a "nice" person Grace is. Edwin is/was the only true friend Ian had throughout school and Viktoria was more a mom for him than Grace ever was.