Nice optimistic nurse want to make something good and important (as she thinks) at that fearful time. She got an opportunity to take a Pfizer vaccine on camera "to help people". So, she took that opportunity, but something definitely go wrong. When she regained consciousness, she was violently pressured to say some bullshit like "I constanly faint every day, it's not vaccine fault" by Pfizer marketologists, and finally she got, that she is completely fucked and will be threatened by corporation to take all the fault for vaccine result.
Just like in ordinal blockbuster movie where some ordinary person occasionally cross some big business road.
So, as soon as they leave her alone, Tiffany do what ordinary person from blockbuster usually do in movies - alerted family and friends to not to give her out to anybody, get rid of the phone, and went on a run.
We all like movies, and I think if we meet with some extraordinary circumstances previously seen only in movies, we have only movie pattern to act as an example.
This theory explain everything (social, weird hospital messages and videos with double, silence from family, etc.) much better than theory that Tiffany is dead. I think there is no any problem for insanely rich corporation to disguise a death as some car accident or something else, definitely not connected to the vaccine.
Can't keep myself from another movie/series parallel: May be, some day, some resistance group hiding from medical tyranny will get a door bell with a girl on the threshold. "I'm Tiffany Dover, come with me, if you want to live!" :)
Idk too, this is just a theory, slightly more positive than theory about her death, and it also does not contradict with known facts.
I also don't know how hard to falsify the data on misc quarry, ancestry or other sites. As a good proof of death I will accept a grave photos from different sources, for example.