Yeah, she probably has it since her name is 13
I think it's pretty clear that she tested positive for it, but wanted a good segue into the thread. The only way they could make her not have it would be a false positive, which would make for a lame storyline.
I looked up the specifics of the disease on wikipedia, and apparently it can have an onset as late as 40-70, depending on the number of CAG repeats in the Huntington's gene (the more repeats, the worse off you are). So I think the show can make a reasonable argument for keeping her as a doctor on House's staff.
That being so, she will definitely provide a new emotional window on the show. Also I think she may be a candidate for dating House, as they are both ailing from illnesses (House's being the chronic pain in his leg). They may very likely start introducing women into House's life this coming season. I think it would be hilarious to see him on dates.