Does she also bark while chasing? If so, you can try a bark collar instead. If not or that doesn't work, get a long distance remote shock collar, let her out and hide. Then just wait until she goes out and chases them or let her out with the cows right away.
Have you introduced the cows to her while she is calm and the cows are calm? My LGD pup only barks and annoys my two lambs, because they are the only ones who won't stay calm around her. My breeding trio will just stay laying and nap, totally ignoring her, so she doesn't bother them.
The chase is always a huge thing with dogs, any dog, if it runs away, it really triggers a primal thing in them.