Hi xParadise! I am experiencing something similar with my doberman puppy, Trinity. She has a bladder infection and struvite crystals and my vet wants me to put her on a Medi-Cal food as well. He said that if I didn't want to buy the Medi-Cal I could buy any good food that had a lot of meat in it and little vegetables. I am currently researching fooods but would suggest you look into feeding Innova's Evo as I prefer a grain-free food as well. The high protein amount in Evo is not recommended for a puppy though but it should be fine for Heidi.
I am curious as to why your vet thinks Heidi needs to be on the special food for the rest of her life? I don't believe this is true unless Heidi has had a recurring problem with her bladder. Once my puppy's infection is treated, I am going to give her cranberry capsules to hopefully prevent it from recurring.
The other question I personally have is will a change in diet actually help my puppy at all? I have read that a change in diet acidifies the urine which only helps to dissolve struvite bladder stones not crystals and that for crystals you shouldn't change the diet unless the crystals are still present once the infection is treated and then the diet should only be fed for 6 months. I am not sure what I think yet but you can research on the internet and check out the following link too:
http://www.b-naturals.com/newsletter...ones-crystals/
You might also want to try giving Heidi only bottled water to drink as tap water can sometimes contribute to the problem. The other important thing to remember is to give Heidi lots of water.
I hope I have been of some help. Good luck with Heidi and feel free to keep me updated on how she is doing.
Edit: Sorry I forgot a couple of things. I have also read that Vitamin C helps to dissolve crystals in the urine. Solid Gold Berry Balance has also been highly recommended to help as well. I am still looking into both of these and obviously you should always check with your vet before changing or adding anything to your dog's diet. If you are not happy with your vet you could always take Heidi to a urologist but I realize that can be costly. I wish you all the best with your girl!