My roommate smells really bad.

My roommate is one of my best friends and we have never had any major issues living together. She is very messy, but keeps it contained to her room so the mess itself doesn't bother me. The issue is she never does her laundry, and her clothes all smell terrible. Her hygiene itself is totally fine (showers regularly, etc.), however she is constantly rewearing the same clothes without washing them, so naturally they start to smell bad after a while. She also sweats a lot, to the point where she has considered botox to help the issue, which definitely doesn't help. Because of this, she constantly smells terrible, but I don't think she realizes it. It's got to the point where it is unpleasant to sit near her because of the smell. The smell also lingers, so it's starting to make the couch, shared blankets, etc. smell bad and I constantly have to wash them because it is so unpleasant and also embarrassing when people come over. Like I said, she is one of my best friends so I really don't want to make things awkward, and I also think her messiness / not doing laundry and other basic cleaning tasks is linked to her mental health, so I want to be considerate of this. In addition to it starting to impact me, I'm sure other people have noticed this including her coworkers as the clothes she wears to work often smell too. I feel like I need to let her know as her friend, but I don't want to over step. Should I say something? If so, how do I approach this conversation?