Once the placenta detaches there's no more nutrition coming through the umbilical cord.
She could have cut the cord off a that point and then let the bees have it (or buried it).
A signal fire was a good idea but not containing it or controlling it meant she might have got herself and her daughter killed by it.
She got lucky - it could have gone much worse.
If I was in labor I would not have attempted to drive anywhere (she left (it doesn't say where) to take a short cut to her parents house) - I'd have stayed put and called for help where ever I started from.
I think I might have done as well or better.
Additional:
I found the article here too - it gives a few more details:
http://www.latimes.com/local/lanow/la-me-ln-woman-lost-fo...
It says:
"Pangborn’s mother, Dianna Williams, told the L.A. Times that her nine-months-pregnant daughter went to a casino on Wednesday to visit a friend and get a respite from the hot temperatures.".
"After visiting the casino, she decided to head home, but she turned on the wrong road and ran out of gas, her mother said. She was forced to give birth to her baby in the forest.".
Yeah, I'm pretty sure I'd have done a LOT better than to put myself and child into that situation in the first place.