I would keep her eating the fitters edge, feed 3 percent of her body weight or roughly 12 pounds if she is weighing 400 and free choice hay at this time in her development. Feed and time will help her get where she needs to be.
Save those supplements for later, if I gave her anything it may be a little of the depth charge and about a 1/2 pound of stabilized rice bran per feeding. If you picked out a good heifer feed and time is all your going to need for a while.
Not knowing how much she is eating now if she is eating less than 12 pounds a day, work her up to it over a few days to weeks, if she was eating 8 pounds I would add about a 1/2 a feeding once she is cleaning it up and not showing signs of it upsetting her digestive system, add a 1/2 pound again, doing this until she is up to the 12 pounds, then adjust the feed as she gains weight to stay at the 3%.
Hope that helps