I currently train two clients with MS. I am happy to say that both have made remarkable progress.
No, I did not do flexibility and cardio. Rather, I strength trained as much as possible and worked on balance as long as it was in a safe environment.
You will probably find that she not only has a foot drop but also problems with hip flexion, as was the case with my clients. Those put her at greatest risk of falling but in both cases I have seen improvement. I’ll be happy to talk to you offline if you wish. You can call me, the contact information is on my website.