I don't use meal replacements. That's because I'm trying to lose weight. MRP are usually very high in carbs. If she is trying to gain muscle and not worried about gaining fat, MRP are great. However, if she doesn't want to gain any extra pounds, then I would recommend her to stay away from them.
Look for good protein powder with very low carbs and fat. She can mix them with skim milk or water depending on her goals. If weight loss isn't an issue then skim or regular milk is ok. Water is better if she is counting carbs.