The tumor is most likely being hormonally "fed". Therefore I recommend focusing on balancing the hormones more than anything. The bitters are a great start, and B vitamins are very important. Phytoestrogens and building up the intestinal flora will also help a lot. If you have a copy of my hormone balance write up have her read it. If you don't have a copy I can send you one.
As for can hormones cause acid reflux, the answer is sort of. Hormone imbalances can cause issues with the gallbladder. Estrogen increases cholesterol secretion in to the gallbladder while progesterone causes gallbladder stasis. Gallbladder issues in turn can cause acid reflux symptoms. The bitter and fiber should reduce this.