There is no law specifically on the subject. The issue is whether or not malpractice was committed, in terms of whether they may be any liability on any impact on a license. There's also the issue of whether dong this violated any internal hospital (or clinic or practice) rules. What she did could create liability, if a patient suffered any harm do it, and again, could represent a violation of workplace rules, affect any medical/nursing licenses, etc. if it was improper to do this, but there's no specific law stating that one nurse cannot change the chart of another. It is a matter that you can and should discuss with the nurse manager, to find out what your institution's policy is and resolve the situation.