Pregnant, can she take ranitidine or not? If not why?!

Antihistamines ok in pregnancy. There is no evidence of adverse pregnancy effect by antihistamines in recommended doses.
Yes, Cat B. Yes, she can take ranitidine (zantac). It's a category b medicine meaning there are no adverse effects on the fetus (in animal studies), but there are no controlled human studies. There is no known risk in 2nd or 3rd trimester of pregnancy. Like all meds however, let your doc know to make sure there are no interactions with any other meds she is taking. I hope that helps.