The first hint is the visual of what happened to her, which mirrors the shield on Logain. The second is that this visual doesn't match what we saw when Logain was gentled. A third would be the wording used by both her and Ishy about being able to sense it, but there being a barrier in the way. The visual is the biggest for me, but the other two make it pretty definitive. We also know that you can tie off a shield and that it will dissipate over time. Honestly, it's hard to imagine it being anything but shielding. They're keeping it ambiguous for the non-readers because it's dramatic, but it seems pretty clear to me.