Hmmm... it would depend, honestly. Is she another relative or just a rando? For relative, I'd aim for an aunt and most likely she would be either similar to Martha in proportions or maybe a tiny bit bigger (for real) or make her kinda like the outliner of the family and make her similar to Lucile in proportions.
As for a rando woman, despite me not particularly prefering less-than-curvy women, a petite similar to Officer Claire would keep the balance between busty and semi-flat.
As for appearance and clothing that's were we could get interesting suggestions. Would the character be eccentric, more reserved, kinda nerdy (despite Vera sorta looking the part due to the glasses and turtleneck)?