When my husband went thru the medical in bucharest they did advice him they test for HEP. However since he doesnt have it and unless someone on here does have it and has successfully gotten thru the interview process after the medical with it i wouldnt know what to tell you. You can however tell your fiance to ask the medical personel prolly at Medsana (if that is where she is going) and ask them. I dont know if it would keep her from getting her visa, i dont see why it would. but then again im not USCIS or the consulate. But yes, they do test for HEP. If you need further assistance, feel free to PM me.
hope everything goes well. and welcome to VJ

this may be helpful to read
http://travel.state.gov/visa/frvi/ineligib...ities_1364.htmlalso
What If the Applicant Is Ineligible for a Visa?
Certain conditions and activities may make an applicant ineligible for a visa. Examples of these ineligibilities are:
Trafficking in Drugs
Having HIV/AIDS
Overstaying a previous visa
Practicing polygamy
Advocating the overthrow of the government
Submitting fraudulent documents
The consular officer will tell you, the applicant, if you are ineligible for a visa, whether there is a waiver of the ineligibility and what the waiver procedure is. For a complete list of ineligibilities see Classes of Aliens Ineligible to Receive Visas.
and i dont see HEP B on the list, but your fiance or you may way to call the embassy, keep anonamous and ask if HEP B which is being treated for can cause a denial in k-1 visa.