Your answer is NOT correct.

GC is based on future employment. If she can prove that her former employer still wants to hire her in the same field and same level, she will be fine. Which law says she has to
work in her field until I-485 getting approval? What she needs to do now is that she has to get an job offer from her former employer which says she will start her employment in the petition field once she has the GC.

If you don't know well, you should restrain from giving
people unsolid info. Thanks!