What happens if you stop chemo?

I know maybe it’s different for everyone

But I have a cousin I am very close to. She is only 34 and has state 4 metastatic breast cancer. She was diagnosed 4 years ago, at stage 3, then about 2.5 years ago, stage 4.

She is having a really really really hard time on chemo. She told me last night she is going to talk to her doctor about stopping chemo, bc her quality of life is great affected

I am so worried, does this mean she has decided to just give up on fighting? Or is there an alternative treatment? I don’t want to ask her, I got too sad when I spoke to her. I am hoping by saying she’s going to stop chemo that means she will choose another treatment, but idk if there is an alternative.