I found an easy way to tame her!

After you prepare your trap (particularly I prefer place the trap on the edges of the top of the mountains, there are less animals to attack you) use one Pteranodon for attract him (of a bite, will make it easier)! The Pteranodon passes through the trap hole while Argentavis is stuck. She attacks the Pteranodon, giving you time to close the gate! I hope it helps you!