Minxy, I know now exactly what makes her creepy.
I looked through all of the CG of the game and now I'm dead sure that the problem is exactly what I thought earlier. Her head/body ratio is way off. I couldn't find any good images with her standing up in full length to compare her body length with the size of her head, but it's clearly visible on many images that while her head is about the same size of her daughters, her body is much-much larger - both taller and wider.
Since on most pictures you can see only her upper body, only her shoulder width and head size ratio looks weird, because compared to the size of her head her shoulders are too wide for a female and she looks like umm... a tranny. Or a cross dresser. Basically, a man in female clothing.
On the pictures where she is standing next to her girls, the girls are only reaching up to her shoulders - she is much taller than her daughters, while her head is about the same size or even smaller.
I guess, she's been visiting a head shrinker for way too many times or something
And considering the age of her kids, she should be about as tall, possibly even shorter than they are.
So, basically, she would look fine as tall as her older daughters are. Or, in case she is a gigantic tank of a woman, larger and taller than her adult kids, then her head should be much larger, too.
Otherwise she looks just alien. Creepy. Wrong.
Some google findings here:
Fashion models are drawn a bit taller