I don't have experience with giardia and my knowledge of it is limited. Wait and see if the next poop is firm. A number of things can cause a loose stool every once in awhile.
I wouldn't worry too much about not eating the kibble. Could be that she just preferred the Stella & Chewy's today. That may also have contributed to the loose stool.
Continue to monitor these changes and discuss with your vet when you go in for the follow up exam.
I'm happy for you that crate training is going well and that she likes her crate.
