Has anyone used magnesium to deal with morning sickness?

My best friend is pregnant right now with her second child and with her last pregnancy she had a horrible morning sickness that was all day every day type of morning sickness right up until she had the baby.  she is pregnant and is dealing with a lot of morning sickness again and I read on Pinterest last time while she was pregnant that magnesium is a good thing to use while pregnant if you have problems with morning sickness. I told her and she never got around to using it but I was wondering have anybody else been successful with using magnesium in like a lotion or other forms to help with morning sickness, and what has been your results if you have used it and it has helped or it has not helped.