Although medical marijuana use in California is legal, it is still an illegal drug per the federal government. Users of medical marijuana in California are not a protected class and cannot sue for discrimination based on that alone. Notwithstanding, given that there is no written lease, I assume the tenancy is month-to-month. If she has lived there for less than a year then you can give her a 30 day notice to move out. If she has lived there for more than a year, then you have to give 60 days notice. If the property is in Santa Monica, West Hollywood, or some other city with a Rent Ordinance you should contact a local attorney, as the rules concerning the eviction notice are drastically different and generally require a landlord to have good cause for eviction.
Disclaimer: You should discuss your situation with a local attorney, as the above statement is a general overview and does not take into account all of the factual considerations in your case. Nothing in this statement creates an attorney-client relationship.
The most important part of your question is "the smoke bothers everyone here." If that's the case, it doesn't matter if your tenant is smoking tobacco, marijuana, opium, or oregano. That fact is, the tenant is doing something that is interfering with others' rights to use and enjoy the property. You can therefore evict the tenant for "nuisance."
By the way, it doesn't make any difference to the analysis whether or not you have a written or oral rental agreement.
Simple - non legal thought:
There are other ways of using medical cannabis without smoking it - why don't you speak with the tenant, explain the problem, and ask if they would consider getting edible forms of the medicine (in now comes in everything from brownies to lollipops).
Best of luck