As others have stated, I think its great that you are asking for help in learning and not just getting discouraged or bitter. Yes this heifer needs some volume through middle, and high fiber products like beet pulp, cotton seed hull, depth charge, etc etc will help to an extent. There are other things to analize that will help change the look of this heifer overall as well though. There arent many "perfect"heifers out there. Almost all of them have at least a small flaw somewhere that we would like to change, some have bigger flaws but are still generally good specimens when viewed as an overall package. I dont know how old this heifer is, but one thing I tell almost all of the kids who ask my opinion, kids I help, at clinics I teach, or when judging a show. It has been my experience that most heifers dont have the same look both years they show. Some heifers are AMAZING calves and tend to dominate their first years, some heifers get outdone their first year but show amazingly their second yr or heavy bred. I think its true that this heifer probably lacks a little of the pizzazz that gives them that little extra flash in the show ring, but down the road I think she will be a good enough cow for you. I think she probably does a lot better in the ring as a heavy bred heifer than at any other time in her career though. From the ground up we can help this heifer a lot by getting her feet trimmed, those long toes will rock her back. Trimming her and getting her up on those toes will give her a lot more presence in the ring itself. While I like a heifer that is long spined, which she appears to be, being long sided tends to exagerate the shallow appearance of one that is a little tight middled. If you blow the picture up it appears that she has a decent hair base, with a little work it could be your best friend. It looks like her belly is clipped pretty tight though, try letting the belly hair grow and pulling it down and letting that add some depth appearance to her. Also as was said earlier if you will clip her tighter from her shoulders forward, not only will it make her look to have more extension, it will also make the front end look smaller which will in turn help make the middle look bigger.
But dont forget that you have a quality heifer, she appears sound, has good bone, and is in good condition. Keep working, keep learning, and be proud knowing you are doing the best of your ability with her.