I think negative IgG testing at 20 weeks post possible exposure is very reliable. It is slightly less reliable for HSV 1 than it is for HSV 2, which is the traditional genital herpes virus. If she received oral sex at the sexual encounter, then she may be at a very slight risk for HSV 1. The test will pick up 91 of 100 cases of HSV 1.
Her symptoms honestly don’t sound herpetic to me. Yes a person with herpes can have some discomfort with urination but there are other things associated with the urinary system that could also cause that. If she has a rash now, she should have someone knowledgable examine and swab test the rash, if the clinician feels swabbing is appropriate.
I do think you can get a western blot in Australia, perhaps. If you can contact Dr. Anthony Cunningham there, he might be able to help you.
But in summary, I don’t think you daughter has herpes but once a person has convinced themselves that they do it is difficult to change their minds.
The blood test with two negatives should be considered reliable – I don’t agree with the sexual health clinic’s opinion.