Because Uber didn't kill her.
It was a fake Uber car, not Uber, the truth is the woman should have been more careful before getting into the car and make sure it was her Uber, not some random killer joe.
Here is Ubers guideline:
Check your ride, every time
Before you hop in, take a second to double-check the app for your driver’s information. Follow these 3 steps to make sure you get into the right car:
Step 1 -Match the license plate number.
Step 2 -Match the car make and model.
Step 3 -Check the driver's photo.
If she did this, she would still be alive.
Her death is not on uber, now if an actual driver hired by uber kidnapped her and killed her while working as Uber, then Uber would be in some trouble.