What are the rules of a women working pregnant when discrimination?

my daughter works for a major store, she is pregnant of twins. what happend was that she first got pregnant, she did not new about, she was working felt pain went to the hospital happends that was a ectopic pregnacy of 14 weeks + a cyst eruption and internal bleeding, she got operated lost the baby a falopioum tube and got clean up was like a secerian, well it seems that the test still was coming up positive for pregnancy they waited 2 weeks did a sonogram and wow she was pregnant of twins this time 4 weeks. well she was suppossed to return to work when she was ready to return and willing they told her that because she could not lift nothing she could not return, well she filled unemployment for children and family purposes. because of that she went back to work, now that she is more in the pregnacy she can not stand long period, had a note from dr. to sit for sort period of time, employer said to her , go back to work when twins are born, that will be next year. what can she do