Julia is described as being a "plump midde-aged woman". She reminds Poirot of a big, fat hen, and he is of the opinion that she is an "empty-headed society woman", and is "selfish, brainless, grasping" and self-centred.
Julia disapproves of her daughter's relationship with Howard Raikes, and brought her to England to get her away from him. She also hoped that Alistair might become fond of Jane, and leave her his money when he died, as he has no near relations of his own. According to Jane, Julia "cadges off" Alistair freely as well.
Julia believes that Alistair is too good-natured, and that it is good of him to let Helen Montressor stay at the cottage on his Exsham estate rent-free, but he should not feel that he has to have her up to the house for dinner every weekend. She says that he should not be imposed upon.
During their weekend stay at Exsham, Julia accompanies Alistair to church, and commands Jane to do the same. At church, she sings in a "firm voice, slightly off the note".