Specifically to block the major metabolic pathways that cancer uses to fuel its growth, the best herbs/ phytochemicals are as follows: Curcumin, Berberine, Luteolin, Resveratrol (or polydatin, from Japanese Knotweed powder), Green Tea and Citrus Bergamot.
However, you might want to consider TCM or adaptogenic herbs as well - Ashwaghanda in particular.
I was diagnosed with de novo Stage IV metastatic breast cancer with metastases to the lymph system, so I've been doing a lot of research on natural therapies. The above are part of my regimen, along with several others for active cancer and the immune system. For your Mom, you might want to look into the therapeutic Keto diet for cancer (significantly more restrictive than the keto diet that's used for weight loss) and fasting for stem cell regeneration.