magnetic case safe for iphone?

If you mean a case with a magnetic closure, no problem. If you mean the case has a magnet in it to attach it to something, that will disable MagSafe charging, mess up the compass, and interfere with the camera image stabilization hardware.

Does your wife have a pacemaker? If so, she should keep the case away from it. Also, it will mess with the compass readings. But, if you don't use the compass, then it shouldn't matter.