What a precious baby. Let me give you the link to A Natural Anti-Cancer Protocol for Dogs, which includes diet.
All of the supplements are effective, but the top two I would recommend are:
1. Colloidal Silver. Colloidal Silver strengthens the immune system and has strong anti-cancer properties. You can put one tablespoon daily in her water or mix it with his./her food. A very high quality colloidal silver and the only one I personally use is from Utopia Silver. They have many sales and are cost effective. If when you order, it doesn't happen to be on sale, you can use coupon code LR001 to get a 5% discount.
2. The second one I would suggest would be Inositol IP6, It also has powerful anti-cancer properties and it is known for shrinking tumors. Utopia Silver has an Inositol/IP6 Product by the name of Cell Forte that also contains medicinal mushrooms. You would mix one scoop in his/her food daily. Again, if this product is not on sale, you can use coupon code LR001 to receive a 5% discount.
Prayers for your baby.