From what I saw in the picture, the cow needs some more meat on her. Her ribs are showing quite plainly, and her hips are pronounced. I would rate her as a 3-4 BCS. She needs more grain to cycle regularly and maintain a pregnancy. A CIDR would be very helpful in getting her to cycle, along with a shot of Lutalyse, and a shot of gnRh at breeding.
A protein block may help you get her into condition. If you can give her access to it in addition to her feed, she can nibble at it as she needs it. I don't think you need to worry about her getting fat at this point. This late in her lactation and in her body condition, you may have some trouble getting her to cycle. Did the vet mention any problems inside?
Spring is coming and that always helps conception.
