What do I tell my GF who has seriously been doing nothing but smoking weed for the last 5 weeks?

I want to tell my GF to stop smoking so much but I've been feeling insensitive to do it since she told me she lost her sister 5 weeks ago. I can just tell by the smell and look that she's basically constantly high now. I want to help but want to let her have her space and I'm just trying to be patient. She's been working and going to the gym about 50% of the time she once was. I want to tell her to stop smoking so much so she can get back out there and get things done. What can I say that won't set her off.