The direction that @Mark_Bailey pointed you is correct. However there is one tricky issue that needs to be exposed to get what you want properly handled.
The Where( :Sex == "F" ) text box is not below the Dist Report structure. Therefore,
dist rep = dist << Report;
dist rep(TextBox(1) << delete;
will not point to Where( :Sex == "F" )
One needs to move to the DisplayBox[HeadBox] which sits above the Report structure in the Display Tree to be able to access TextBox(1).
Below is the syntax of the JSL to accomplish what is needed
dist = dt << Distribution( Continuous Distribution( Column( :height ) ), Where( :sex == "F" ) );
dist rep = dist << Report;
(dist rep<<topparent)[textbox(1)]<<delete;
Another way to access Where( :sex == "F" ) is to access it from the actual window reference
window("Big Class Where(sex == -F-) - Distribution")[textbox(1)]<<delete;
Jim