The base path rule is the entire reason it's not interference. She takes the direct route to first base after completing her bunt. She was never outside the running lane; because the running lane starts after the base path has been established, and therefore is meaningless.
While you are correct it is not interference, your reasoning and description of the running lane are completely incorrect. The running lane begins 30' down the line between home plate and 1st base, is 3' wide and runs parallel to the 1st base line in foul territory. It has nothing to do with the runners basepath.