This is a risk-reward situation. If you are more about morality and ethics you could tell her before hand, but risk your job at hand. Or you could keep to yourself for your own best. I would suggest her the job without including the layoff, as it keeps you under safe ground and if she takes the other job, automatically removes one potential person to be laid off. This would increase your chances of keeping your job rather than being fired or laid off. The risks professionally would be your own job at risk, and personally your own morals/ethics.