Hi dvovan,
I have the same timeline with your sister. They received my application on July 7th and started processing on July18th 2011, after I received the AIP through email that stated I had met the requirements on Aug 2nd 2013, the information on ecase was changed to: they started processing since Aug 1st 2013, your fmaily will be contacted.
So don't worry about it. Just wait or do something for it such as asking MP for help, or apply your nephew's visitor visa. Have it a try.
My dependant didn't receive the LC2 kit as her student visa got refused twice so I hired a lawyer to get the judicial review, and my daughter is here now. So I updated my information after my daughter arrived and asked to process inside Canada, one month later, I received the second letter stating decision made, last week I received the letter and I was scheduled the interview on May31st, on my daughter's birthday.
Since your sister has an open work permit, so try to apply your nephew's visitor visa or student visa, it takes faster than waiting for the kit.
Good luck to your sister and nephew.