Breast cancer early signs ?

Okay I’m writing this because I’m scared and concerned for my mother. She’s now 42 but at 40 she was told by the doctor of an alarming thing in her left breast. She just told me this a few seconds ago which left me in fear... she said she was suppose to do a 2 year check up but refused to. Her way of dealing with this is cutting out sugar and doing small exercises... can someone please give me advice