Well, due to her lung issues, she shouldn't be smoking or vaping anything, ever, full stop.
But it's actually worse for her because THC -- smoked or eaten -- can engage in all kinds of fuckery with your blood pressure. Your blood pressure can spike if you're lying down and then drop when you stand up, for instance. Normal, healthy people either don't notice these effects or else just get a bit of a headrush/feel their heart start pounding randomly when they're high, but for someone with hypertension it can be a problem. Also, as far as I know, Warfarin is one of the very very few pharmaceuticals that's known to directly interact with THC. This might be part of the reason why she was taken off Warfarin (or was she? I can't keep up).
As far as whether her doctors would need to take this into account, I'm guessing they'd tell her to lose the vape and otherwise want to proceed with caution and monitor her closely -- if she's honest with them about being a regular pot smoker/eater, that is. I'm sure she lies to her doctors about most things, which is probably why she isn't on more medications/hospitalized for more things/sent to more specialists than she already is. Mind you, she's completely non-compliant, so maybe there are more pills/procedures/specialists in her life that she's just ignoring. We know she blew off her colonoscopy when she decided fasting for a day was too dangerous to her health or whatever, and that she'd rather take her chances with colon cancer than skip her weekly McDonald's binge.