is it possible and winnible to sue the tobacco companies over a death caused by second hand smoke

It is impossible to answer your question without a full understanding of the facts including exposure of your mother to other potential causes and in particular, to second hand smoke. However, there have been successful cases brought on behalf of workers exposed to second-hand smoke in the workplace for example. You should contact a plalintiff's firm in Los Angeles dealing with these types of cases. You can call the local bar association for names of plaintiffs' firms or look online and find out the ones who handle these types of cases in LA and set up a consultation with them. There are one or two large, well-known plaintiffs' firms in LA/Santa Monica that would be a good place to start. Check in Martindale-Hubbell under Los Angeles plaintiffs'/personal injury firms, products liability firms. Check with the California State Bar also. Keep in mind, you have to prove exposure and causation - which can be quite difficult depending on the facts.
Disclaimer: Please note that this answer does not constitute legal advice, and should not be relied on, since each state has different laws, each situation is fact specific, and it is impossible to evaluate a legal problem without a comprehensive legal consultation and review of all the facts and documents at issue. This answer does not constitute an attorney-client relationship.