Crystals

[Viridiana]

Not if you watch the cut scene it immediately happens after she tries to temper us the blessing protects us then as soon as it goes away the blessing shoots out at her and hits her dead in the chest. I don't know if I would call it feed back but it definitely is something that hits and hurts her to pull it out.

Yeah, I look at it more as strike->counterstrike. I don't think the strength of the return stroke (pulling out the Crystal of Wind) had anything to do with the strength of the initial attack (attempted tempering). As for why throwing off Garuda's tempering attempt drew out the Crystal of Wind when it didn't draw out Ifrit's Crystal of Fire, I have two things probably contributing to it. First, if we really must prove ourselves to the Crystals as Hydaelyn tells us, throwing off Ifrit's tempering proves nothing of ourselves. Defeating him shows that we have the strength and will to face the Primal threat. Against Garuda, the events are in the opposite order. We defeat her first, but it's hard to draw a Crystal out of a Primal actively using some of its aether (though I sincerely doubt either Primal had truly tapped into the aether of the Crystals of Light). Having already proven ourselves, when the power of the other Crystals shine through the tempering effort, the Crystal of Wind is drawn out.

Edit: Then I realized I said I had two reasons and only put one. Second reason: We're just plain stronger. Granted, so is Garuda, but when it comes to beckoning to Crystals of Light, heart matters as much as strength.