-Reduce her damage. She can cleanse herself but lose a turn or she will deal reduced damage. For example, Monolophosaurus.
-Tank her. Shield is a great counter for Einiasuchus, even a short one. Nodopatosaurus seems to hold great against her after the update. If you use Nodopatosaurus, the best combination seems to be Slow - Shield - Slow - Armor piercing impact - Slow if she cleansed herself or Shield if she didn’t
-Stun her. As mentioned above, Stegoceratops can deal with her unless all stuns fail.
-Remove positive effects. If you have a fast dinosaur with nullifying attacks, they can reduce her damage a great deal. Again, a good example is monolophosaurus, but Tanycolagreus can work too.
-Gorgosuchus and Postimetrodon are also good ideas. Both work in similar ways as Einiasuchus but are faster and can pierce through armor, should make fast work of her.
Einiasuchus is a great dinosaur because she can deal great damage, survive good hits and be very versatile so she can be annoying but as you can see, there are many techniques that work against her. Lastly, someone above recommended Allosaurus and T-Rex. I do not recommend this. Unless you get a great crit, Einiasuchus can take them down easily. You need to either be faster than her or be able to stun/shield against her to survive.