It depends what type of condition she is in and how fast you want her to gain weight. I used to feed mine 16% protein grain (amount depended on age and condition) and lots of good hay, minerals/salt if they wanted and needed it. Make sure she gets plenty of exercise and green grass is always good of course.
You have to be a lot more specific. How old? what does she weigh?
If you are talking about a weaned heifer, she should be getting about a 15% ration, with plenty of good quality grass hay, minerals & water. You start her out at 1% of her body weight per day (split in two feedings). Weekly increase her grain a little at a time, making sure she cleans up each feeding within a short time period. Watch her manure. You don't want it too thick/hard or too runny. Too hard, she's not getting enough protein - too loose, she's getting too much - OR - you made her sick with too much grain. I feed all the good quality grass hay they will consume. I keep it in front of them 24/7.