What is helping Lara?
Solution 1:
Lara has luck and the script to help her. Himiko controls weather but is not precise with it, otherwise, she would have fried Lara on the first encounter. Here is what the wiki says about it
Most sinister of all, Himiko's consciousness manifested itself in constantly stormy weather surrounding the island. These storms were unnatural, driven by her rage and consciousness, and would actually vary in intensity, to deliberately cause any and all ships and aircraft that ventured near the island to be wrecked or crash on it.
For the Stalker Stormguard, it is luck again
After a massive battle against the stormguards, she comes to face the stalker, however the strong winds blowing some wooden fences knock him out of the way for Lara to continue.
Himiko clearly knows that Lara wants to stop her from transfering her soul in Samantha's body.