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My sister was working at a place with all men and her.
She has been there for 2 years. She received certifications
and advanced. She was on a day shift job. Her boss did not like here
and told the men to work her *** off until she wants to quit. Since that
didn’t work he told her she needed to be on evening more. So he replaced
her day job with a temporary person (man). Its been an on going thing....finally she quit like he wanted last week. Everyone at the plant knows he stated he wanted her to quit. Is this discrimination??

It sounds suspiciously like discrimination on the basis of gender. Was the boss who wanted her to quit the same person who hired her? If that is the case, it makes the argument that it is discrimination a little weak.

No,

A different man hired her. He left about 6 months ago. And the job was replaced by him. He had always been there but was moved up after this other guy left.

Then, she may wish to seriously consider filing a complaint of discrimination against that employer. The link I gave you earlier, eeoc.gov, will give informaiton on how to file a complaint.

Good luck and let me know if you have any other questions.