Answer:
it had such a great appeal that drove her crazy.
Step-by-step explanation:
The author uses the phrase "killing power" to describe the eyes of her secret love because it had such a great appeal that drove her crazy. It made her feel light-headed and dizzy making her almost fall into the ground.
The author always felt that her secret lover had the most mesmerizing eyes and when he looked straight across the room and into her eyes, she became breathless.
Thus, the phrase "killing power" helps in expressing how she felt when her secret lover looked straight into her eyes.