I have no experience with Giardia, but I was reading this and hope it will be of some help to you. I'll leave the link as well, so you can see where it came from.
I had a rough time with giardia at my house. I believe Juju had it when I got her. Then, Betty got it. They were treated...tested negative...but still had symptoms. The vet sent the next sample to an offsite lab. Giardia was still present. I paid several hundred dollars between testing, meds and office visits. And I'm still not positive it is gone. If you do get her, just make sure that she has been treated...clean up the bathroom area very well, with bleach if possible, because the pup can also reinfect herself. You also have to clear her tail end often. It's not always this hard to eradicate, but it can be. And be aware that the test that the vet performs inhouse is NOT as accurate as the one is that they send to a lab. So, even if she tests negative, check the stool daily because that is a better indicator. Good luck. I'm not trying to disuade you from getting her, only to let you know that you do have to be vigilant.
Giardia?