Its called SIN(social insurance number) and it is required for employment, all the taxes paid by an individual to Canada Revenue Agency are through this number.Thank you so much for confirming this.
I believe that SID stands for Social/System Identification Number issued once the person becomes the PR process.
So according to your reply, once she completes the landing process (which takes approx 1 day) and obtains the proof of residence over there like bank account ( which may take 1-2 weeks) or the postpaid connection (might take 2-3 days) or a residence contract( might take 2-4 days), I would be immediately able to claim the 15 points for sibling.
Kindly let me know if I miss any important detail in this and also let me know about any other fast means of obtaining proof of residence over there which is recognized in the express entry process.
I know because I m working in Canada on Post graduation work permit. It can be applied any time after landing and takes around 10-20 minutes. But I m not sure is it enough to make you eligible for 15 points.