Did Domino Really Have HIV?

I'm watching this movie again and was struck by something that I found quite interesting. When Bill goes to Gillespie's Diner and talks to the waitress, he deliberately lies to her in order to find out where Nick is staying. He tells the waitress "Listen, to be perfectly honest, it's a medical matter...some tests, and I know he'll want to know about them as soon as possible". This is an obvious lie with an added twist of irony when he prefaces the statement by saying "to be perfectly (dis)honest".

Later, when Bill goes back to Domino's apartment, Sally tells him that Domino got the results of a blood test and that she is HIV positive. I found this rather striking. If the mention of "tests" is a ruse first perpetrated by Bill, is it now being used against him by Sally? For what reason?

The scene itself is very strange. It explodes into sexual tension, almost for no reason. Bill enters the apartment and immediately undoes Sally's shirt. He fondles Sally's breasts the same way he 'examines' a topless female patient in an earlier sequence. Again we see a doubling--the doubling of the 'examination', but also, perhaps, the doubling of the lie (medical tests). After Sally tells Bill that Domino has HIV, she offers him a cup of coffee. Again, this is another parallel of the earlier diner scene, when the waitress serves Bill a coffee just before Bill lies to her.

So if Sally is lying, just as Bill was earlier, and Domino does not have HIV, then where is she? Was Domino at Somerton? Did she offer herself as the sacrifice? Who is Sally? When Bill arrives with Domino, she claims her roommate (Sally) is out. Was Sally already at Somerton? Is Sally lying to Bill to protect her 'friends' at Somerton?

As with virtually every other element in this film, it seems to dissolve when logically scrutinized. Everything seems to dissolve into a sort of vapor, the same way a dream dissolves from your memory upon waking.