Her chances are very low for a good number of reasons. It's all an educated guess from my perspective.
HIV is definately among the most lethal viruses in recent history but it is also a remarkably fragile virus that is vulnerable to changes temperature and surroundings. The virus is destroyed within a matter of minutes upon exposure to air, water, and cooler temperatures outside the body.
The combination of exposure to air, dilution and being killed by water, as well as the ambient temperature being well below 98.6 degrees COMBINED with anti-viral medicines would drastically reduced the virus's ability to infect someone by means of broken glass.
I was also rather ticked off at the situation that she was put in. I mean, if you research crime-scene clean up crews, they ALWAYS use bio-hazard suits, and will put any blood or body-fluid soaked, clothes, furniature, and other items into bio-hazard containers or special bags to be incinerated.
They will have likely not allowed Stella and the CSI's in to examine the guy's body without notifying her and the other CSI's of a potential pathogen.
Anyway though her chances of being HIV-Positive are very low, other more infectious pathogens should be of greater concern. Bacterial or non-HIV viral infections such as syphilis, herpes, typhus, gonorrhea, dengue fever, or even other lethal diseases such as malaria or West Nile should be of greater concern.
For everything that AIDs has caused, it pales in comparison to the davastation that malaria has caused in much of Africa, even in places that have not been hard hit by the AIDS pandemic. While not trying to change the subject too much, malaria is one of the deadliest diseases of all time and before quinine and antibiotics were developed, many Europeans didn't even consider Africa habitable until these medicines were developed which made conquest and colonization possible. Malaria has davastated many areas that even AIDS has not (yet) been able to do. While education has proven to be useful against AIDS when done right, malaria is far more communicable and should be a concern.
That said, Stella while understandably terrified of the possibility of acquiring HIV (not likely), malaria, and syphilis should be of greater concern. If Stella actually tests positive for HIV, it could very well send CSI: NY into the abyss. I know it's just TV but the whole prospect of seeing a great charachter waste away over time is too much for me. If she is positive, I swear I'm going to mentally discard all continuity after "Run Silent Run Deep" and write my own timeline fanfics from now on.
