People with lives, jobs, kids, more important things to do, don't have the time (I certainly don't have the time to play football twice a week!), money or help (she'll have a personal trainer) cannot simply 'put some effort into it' to look like that. She's probably been skinny all her life - it'll be in her genes.
LOL that old chestnut.... 'genes'
Also I work in the City of London and area where people work far longer hours than most of the population and yet plenty seem to manage to exercise and eat healthily. In fact obesity is more common amongst lower income groups, a larger portion of whom only work part time or don't work at all and so have ample time to exercise should they have the motivation to do so.