Nobody can say for sure if weed will help your mom's condition, but it might bring you two a lot closer! Or, it could tear you two apart. Make sure she would really be okay with you asking her to smoke with her. It sounds like she'd be okay with it, but you can never tell. Maybe first ask as a hypothetical first.

I wish I could smoke with my mom, but my parents would kill me if they even knew I smoked. Snoop used to smoke and drink with his mom (of course that's not very surprising), and many of my friends smoke with their moms too. I'm so jealous