I'm not sure what 'lazy' means but Catherine sure as heck isn't lazy no matter what royal standards you judge her by.
Catherine is married to a grandson of the current Queen,it was announced on the their very engagement day that the couple would not be undertaking full-time 'royal duties'until Williams military career is over. Who would expect Catherine to be a 'working' royal when he husband is not?
But lets come to to what Catherine actually does do , she is patron to 4 very important and personal charities that she picked herself and believes ins.
As a 'third' of the Royal Foundation of the Duke and Duchess of Cambridge and Prince Harry , Catherine is helping raise and dispense millions £ each year to dozens of worthy organizations and causes.
I think she is doing exactly what is expected of someone married to a high-profile but still junior member of the BRF.
W&C are focused on their married lives for the first couple of years and all the while work at their individual charities and Royal Foundation. I would judge her differently if she was married to a Crown Prince or even one of the Queens sons but as she is not, the workload she undertakes is more than enough IMO.