Normally you want to kill minions fast, but sometimes you can´t. These are the moments this card gets insane value: being able to prevent two activations of a minion is great. This card synergy with cards like Press the Advantage is great and there are not many cards to deal stun or confusion anyway. Furthermore, Spider-Girl has 2 atk so even if you can´t use her ability you are getting 2 damage and a block, and that´s ok. If this card were a 1 thw and 1 atk I would play it anyway, so that tells you the value of Anya.
Attack: 2. Thwart: 1.
Response: After you play Spider-Girl from your hand, stun and confuse a minion.
"Alright you bunch of losers. Who wants a piece of me?."
The Rise of Red Skull #40.