Spoilers for episode 1, but anything up to episode 4 is fair game.
First off, she died.
However, what exactly killed Helen?
My interpretation is that Helen joined the hive mind, but her body/mind ultimately rejected it causing her death.
Helen’s joining process was slightly different than most people we saw. When people were first infected they largely seized in place and did not fall over. As Carol is exploring the bar everyone (that I can remember) is standing or maybe squatting, but maintaining their balance. The same is also true when Carol arrives at the hospital. The doctor she tries to talk to us standing and maintaining their balance.
Helen however, fell over. Did the fall onto the pavement kill her? Is the reason she fell/couldn’t maintain her balance the same reason she couldn’t join? Was/is Helen’s inability to join a hint of how to unjoin? (Although I don’t know what that hint is yet.)
The hive mind didn’t make any distinction about those who died the day of the joining. If their death was caused directly by the joining or if it was an accident as a result of everyone being unable to move.
To add to this, when we first see people joining the hive it is the result of direct contact, specifically saliva. However we later see airplanes spraying cities, implying that it is airborne. The hive also talks about working on making the virus compatible with Carol. While they may have started after hive day, did they perhaps also start before?
If no one died during the initial joinings, but people died during the mass joining, how can they be sure they won’t kill Carol when they force her to join?
Intra cranial bleeding. In her last moments you can see the blood clots spreading under her eyes. The attention to detail is astonishing.
So is that caused by the fall, or by the joining?
I’m guessing by the fall.
The deaths caused during (and after) the outbreak have only been shown so far to be coincidental injuries caused by people suddenly having seizures at inopportune times.
Helen is standing when she is infected, and is shown falling and hitting her head hard. In her last moment of lucidity, she appears to have that same sense of bliss as the other infected, indicating that the infection itself was successful, but she likely died from the head trauma caused by the fall.