It sounds like your coworker is going to be laid off regardless of whether you stay or go. Don't punish yourself over a decision you did not make and cannot influence. Take the job you want the most, wish your coworker good luck and don't look back. Unfortunately, there is no room for loyalty to a friend and concern for what other people think of you in today's job market. After a few months she will probably have forgotten about you and moved on with her life. Move on with yours.