Elena, from your description I feel pretty safe to say you have nothing to worry about. I am one of the lucky very few people who have been introduced to what is called the 'Death Touch' - or Dim Mak in Chinese - in martial arts.. My teacher was a very traditional master who started his studies as a child back in the 30s in monasteries in China, he was the top student of his class later the inheritor of the entire style - what is in martial arts called the 'generation master'.
What the person you described above did to you is nothing at all what the art of 'Death Touch' is. Having a 'warm feeling' after being hit is normal for just about any hit to the body, this is the body's normal, natural reaction to physical trauma - trust me I've been hit a few times in my life during my martial arts studies - and also the nature of the hit tells me that it's nothing that would be related to the 'delayed death'.
I do however would like to ask you a few questions just to be on the absolute sure side: where EXACTLY were you hit? Was it the dead center of your body or was it to either side - even just half an inch matters!)? If it was to either side, which side and how far off your center? Please be very precise. How far down from your sternum was the hit, can you measure it for me? Did you receive multiple or just a single blow? Sounds like this was also a very hard hit, please confirm that it was a strong hit. What day AND time of the day were you hit (date and what time - around 10 am, noon ... etc.)?
Other questions: have you had an X-Ray/CT scan to eliminate any internal injury or bleeding? With a hard blow such as that, I would worry more about an internal injury, not the Death Touch. If you haven't yet, please get one (or both) of the above done to be safe.
In conclusion: from your description I feel safe to say that you have nothing to worry about as far as the 'delayed death' goes, this person is just a crazy dangerous person with no skills or knowledge of this art (it is an astronomical chance that some punches without skills would work but in your case even these can be eliminated). Just please answer all of my questions but again, I see no reasons at all for you to worry beyond internal injuries. I also do hope that you have reported this person to the authorities and she is dealt with according to her actions.