Lets start off by saying HIV/AIDS isn't as much of a death sentence as it used to be. Science is on the verge of a vaccine and is working feverently on symptom suppression. Some diagnosed with the disease live to be in their 80s.
Secondly, it takes TWO TO TANGO. He has almost as much responsibility contracting the virus as she did giving it to him by not wearing protection. The article also doesn't give specifics as to when she contracted the disease herself, and when she realized she had it herself. She could have contracted it a year ago, had sex with this guy 6 months ago, and not found out until yesterday. Meaning he would already be infected. Timing is critical.
Which brings me to 3. In order to be charged with criminal transmission of HIV in the US, which is only a misdemeanor in most states, you have to prove intent. If they had sex 6 months ago, and she only found out yesterday, there is zero proof of intent. Again, timing is critical.
Criminal transmission of HIV - Wikipedia, the free encyclopedia
And how about the hypothetical? What if he stabs her to death, and next week they come out with a cure for "early-onset" HIV, which isn't entirely out of the realm of possibility?
So no, in all seriousness, I can't say that she deserved to be killed. Hyperbolically, there's a bunch of people I want to murder, like the guy that pulled out in front of me and proceeded to do 20 mph under the speed limit.