If I weighed another two stone, had a bigger bosom and looked more maternal, people would be more sympathetic.I don't think it has anything to do with how she looks, but rather it's how she acts.
I think it's because a lot of people don't think she acts maternal that they're somewhat unsympathetic. What her mother describes as a "terrible mistake" (leaving the children while she & her husband dined in a nearby restaurant) a lot of people see as pretty close to neglect.