Prayers and healing energy coming your way and your mom's way! I am so sorry she is having to do battle with this.
One thing you should know is that chemo has come a long way, even in the last 2 years, esp. since they can diagnose the many many many "kinds" of cancer and target it with the regimen they know will have the best response.
You need to stay strong and positive for your Mom, she sounds like a strong woman.....and a smart one (she raised a very caring thoughtful kid.....you!) and trust her doctors and team to get her well......and believe me they will give her their very best.
A family member is battling triple negative breast cancer right now, and she is still young, so my heart goes out to you, because it's hard not to think about it all the time and get over the shock.