Gonzo got somewhat obsessed when I had bunnies too... he never smashed their cages, but he started to constantly want into my room to watch them. Border Collies are the greatest, but they're freakin insane sometimes !!

What I would do is just cut off her access to them completely ~ try getting a lock on the door and just locking it, OR if you can do so, move the animals to a different room which is easier to secure and that Happy can never be allowed into. Don't react when she's pacing in front of the door... it will just feed her obsessiveness. Hitting her will also make her even more obsessive. Try teaching her a very, very solid "leave it" command, and use that when she's pacing. When she leaves the door, reward her with a treat and play with her outside. When she's acting high-strung and really reactive, a bunch of exercise and training might also help calm her down. Some people would say desensitize her to the aniamls, but it sounds like she's beyond that and she has too much instinct to safely be around the animals. I think she'll just forget about them if they're completely kept away from her for long enough