50/50 is nice. The alfalfa gives her the added nutrition and the grass gives her something to do. Oat hay is a popular option that can't be overlooked. Most horses love it. The alfalfa should also decrease your need for adding concentrates. The problem with G/A blends is they can be all over the place. Some bales out of the same field, same cutting can be 10/90 while others are 90/10. I like to buy straight G and straight A so I can control the blend. Because G and A also tend to mature at different rates and optium cuttings are very different, it gives you the ability to buy it the way that works best for your situation.
I have had to feed only grass, only alfalfa or somewhere inbetween. Don't be so set in what you feed that you don't take advantage of what's a good deal and available. The pelleted products that she is being fed (G,A and BP) are all forage replacement products that can be convienient to haul and store but often cost twice as much as the equivalent in hay. I'd get her switched over to mostly hay and just use the pelleted products as fill in (plus the Vit/mineral).