Ok, I see what the problem is... Well if it is the dreams taht bother her, I think there are 2 main options here:
1- Consume (in whatever way- smoke, eat in a dessert or any other way) weed ( I have not read about these effects of the drug, but if you did your research and are confident that it causes people to not dream, I guess it can be a solution to her problem).
2- Go to a special psychologist ( to have a conversation with her and see what the problem is. These professionals are not to be visited by the mad, they are to be visited by everyone. They can understand the human psychology perfectly (maybe not perfectly, but far better than any other professional) and can try to get your mother rid of what is bothering her on a subconcious level). There are many specialsts known in this field- 1- Psychologist (also known as therapists), 2- Hypnotist (someone who can put your mother under a deep state of concentration (also known as "trance") and therefore have PARTIAL (definitely NOT absolute, THOUGH, it depends on your mother's subconcious whether she fully trusts him/her (the hypnotist) or not) control over her to induce suggestions such as "You are not going to have any dreams from this moment on". It is not popular (this profession), but it is indeed real and effective (I have read a lot about this as I wanted to be a hypno-therapist myself, but that was years ago). Do a research and see what you can find about such kind of therapies. Many people report to have stopped smoking, reduced drug intake, lose bodyweight etc. using this method. Do your research and see if it is "trustworthy" yourself), 3- Hypno-psycho-therapists (these people are specialized in both human psychology and hipnosis and are by far the ones that can either correct or mess up ones mind. I am sure that if you do your research you will find more info on these professional therapists).
Weed might be a temporary solution (as it is not the root that will be treated, but the surface only). Dreams are absolutely psychological and only psychology or mind related therapists can treat that (I think). This is the advice I can give you, I hope it works! Good luck!