@judychurch, This is understandably a difficult time for all of you. I don't have children of my own, but I do have a mother, I'm 54, and I have metastatic lung cancer and stage 1B breast cancer. We are all different, and what we want from others around us is different too. I'll share my perspective, which may or may not match your daughter's. During the early days after diagnosis, we are going to appointments, following the plan, and doing what we're told. Our heads are spinning with a new language of cancer terminology, and we may be emotionally numb. Try to focus on that next step, the next appointment, try not to get too far ahead of yourselves, and try to not jump to conclusions about treatments until you have a doctor explain the options. Our minds like to jump to the worst-case scenario, but that's never helpful, and often not applicable.
You mention being strong for her. This can be a tough balance. She'll need you to sit and listen when she's ready to talk. She also may benefit from seeing your vulnerability. My family is a stoic group (me included). The first time I saw my mom and sister after I was diagnosed (during covid lockdowns, so it was months later), I was the only one that showed emotion. They tried to be encouraging, but I felt like no one understood the gravity of the situation because they only had positive things to say. I know now that they were trying to make me feel better, but at the time, we can feel like no one understands and that can make it easy to shut down and stop sharing too. Be sure to listen and empathize with what she's going through. Ask her what she needs from you; just someone to listen or someone to try to problem solve.
Treatments for cancer today, even metastatic cancer, are vastly improved over what they used to be. There is a lot of hope in the breast cancer realm. Don't be discouraged. It won't be easy, but treatments today are very effective. Please keep us posted.