Hi Zopen,
When the corgi is chasing the aus.shep. as soon as you see her start to become to excited, reprimand then step in and leash her if you can (don't use your recall as she will learn that coming when called means end of fun), by doing this you end the fun, and control when it starts again. The fun shouldn't start again until she is calm and seated, then you can praise her and release her with a release command like "free".
When reprimanding, DO NOT yell, as this has no effect on a dominant dog. Growl instead, use a guttural growl like " AAHHH!" instead of "No!", as this makes a sharper sound then "No" (If done correctly it may hurt your throat a little). The aim is to give her a shock and let her know what she is doing is unacceptable.
An alternative if you can't catch her in a decent amount of time after your reprimand (within a few seconds after the reprimand) you could try keeping the garden hose out. Reprimand and soak her with a jet of water when the behaviour begins. If you don't have a hose, you can use a bucket of water or a heavy blanket for the same effect (you'll just need to have a good throw

). The idea is to stop the behaviour before it escalates to a higher level of energy/prey drive.
And remember,
always praise enthusiastically any playing that is gentle and not aggressive!!
Hope this was of help!
Blue