Can radiation for breast cancer be given to someone with Lupus and Fibro Myalgia?

Once again, this is sad, but supposedley my mom also has Lupus, and Fibro Myalgia(sp). Would this allow her to still go through radiation and work all the time and drink all the time. five years ago she supposedley needed a kidney transplant or she would die. Now, with still her own kidneys, she is an alcoholic, she drinks to dull the pain she says. Also, I was reading a website on BC, and it said that chemo is usually done before radiation. My boyfriends mom did radiation first, then the chemo, and all of her tumors are pretty much gone, thankfully. Again, only serious answers please, and thank you.