Creating Report without Sharing Sheet - I need help!

I am trying to find a solution...I have tasks related to confidential legal matters that are in a smartsheet. As I am breaking those matters down into tasks within the smartsheet there are some tasks that are not confidential and I need my administrative assistant to complete them without being privy to the broader issue at hand or being able to see tasks that do not pertain to specifically to her on the sheet. How can I keep all tasks related to a matter together but only have my administrative assistant be able to see and address the specific tasks that relate to her?

I created a report that pulls only her tasks out of the smartsheet, however, since I haven't shared the underlying sheet with her the report looks correct on my side but when she logs in it is blank. I know that I can share the whole smartsheet with her and that would make the report work, but I can't because there is other information contained in the sheet that she cannot under any circumstances be able to access.

What am I missing?