Since you are supplementing the cows, no, do not give her anymore protein. Most beef cows, ours included, get little if any extra above the free choice hay, in the last 2-3 months of pregnancy. Too much/too hot of a ration will actually be worse than skimping. The calf does it's most growth of size/weight etc in the last 60-90 days. You don't want a 150 lb calf... you want the cow to be drawing on her body reserves to help the calf develop those last couple of months so she is not feeding it "too well". Granted, you don;t want them thin or drawing on body reserves to the point that they get out of balance and get milk fever.... and yes beef cows can get it. It is the body pulling too much calcium from the bones into the bloodstream and mostly happens to dairy cows but also to cows that have an unbalanced ration. Gets the calcium/mag/potassium out of balance. With your supplementation, she ought to be fine. You do not want her to be too fat or she could have calving problems, and you do not want her to have a fatty udder, again from too much "good food" which puts fat into the cells. Many times a beef heifer will get a fatty udder at a younger age if she is being fed too well. Fat cells in the udder can reduce the milk producing ability.
It just goes to say that you want them to look good, but not be roly poly.....
Just like women are encouraged to be fit and healthy..... not sit around and eat for 2 (or 3 or 4) so to speak.
After she calves you do not want to up her feed either for a bit. She does not need to start out producing 5 gallons a day.... a beeffwill drink frequently and small amounts.... a pint or 2 at a time for the first few days.... but they might nurse every hour or 2 or so.........This way they stay full, the 1st stomach (true stomach that digests the milk) will be stimulated to work without flooding it. That is why it is better with bottle calves to keep them a little bit hungry for the first few days.... smaller amounts more often will help prevent alot of the scours in calves. I want them to be wanting more milk than to seem full.... The more we mimic nature, the better off the calf is. It seems to be a hard lesson to learn and apply.
I think you will be just fine. Cut back their feed... do it over a week or so, just a little at a time. If you really want to feed twice a day, then in a week or 10 days they should be getting half.... but if possible you might want to get the younger ones separate and let them have a little more and the mature ones less....
You also need to get the bull out when she is ready to calve. Since you have just a few cows, he is going to want to be right there and the calving hormones/smells will cause him to worry the cow when she wants to be bonding with the calf. Most cattleman that don't take their bulls out, will usually find that the cows that are calving go off and find a quiet hidden place to calve and will stay there for a day or 2 so they don;t have the distraction of other animals. Helps the calf bond with their own momma. I have had some cows that are such good mommas, that when they are waiting to calve, they will try to take over a calf that is not their own and it can cause problems for the calf to figure out who is really it's momma. Not something you need to worry with right now... but the others may be more in the way than not, if she cannot get off by herself to calve.
she will be along in the early evening 
