okay, so me and my friends almost got into a fight over this, so i desperately need a ruling. if invisible girl (R) is in hindering terrain, does she pass that 19 defense to adjacent characters, or is it still her 18 defense?

She only passes the 18 DV. The +1 for hindering terrain is a bonus when being attacked. That bonus does not transfer with the Defend super power.

If I'm right Defend only ''transfers" the printed value on the dial.