This condition is known as hyperemesis gravidorum,in common language ,pregnancy induced vomiting s, It is seen in 4 percent of pregnancy and is more often persist for first 3 month of pregnancy and will resolve over period of time,She has to take care of good hydration,not to allow lose water from her body.I am sure she will be on folic acid and vitamins and calcium supplements.Color of tongue may be either due to deficiency of vitamins or stain imparted by drugs.If vomiting persist she should seek obstetrician consultation and need hospitalisation.Mean time ask her to take high carbohydrate diet like buiscuits with tea etc and folic acid supplementation.