I was expecting to see something really gaunt and scrawny. Yes, I think she needs to be fed well, but I've seen other cattle in far worse shape than that.
Don't know your setup. I guess I'd probably keep feeding them together so they've got a buddy and put the bull in with them, depending on when you want them to calve. Are you concerned that the bull will hurt her when breeding (you said "she might not be able to handle him")?
I realize commercial cattlemen want everything to calve around 2 years old, but with mine (Dexters) I'm not so concerned about that and have found that a few do better being held back (and the ones that have bred a little older the first time are usually better mothers).