In California, you are entitled to cut back the branches which encroach over your property. However, you do not have the absolute right to cut or remove branches from your neighbor's tree. In the case of Booska v. Patel (1994) 24 Cal. App. 4th 1786, the California Court of Appeal held that a neighbor does not have the absolute right to cut encroaching roots and branches so that they end at his or her property line. You must take into account the health of the tree before you start trimming, cutting or chopping. You might be liable for reasonable costs of replacing destroyed tree with identical or substantially similar tree.
Frank W. Chen has been licensed to practice law in California since 1988. The information presented here is general in nature and is not intended, nor should be construed, as legal advice. This posting does not create any attorney-client relationship with the author. For specific advice about your particular situation, consult your own attorney.
If your neighbor refuses to correct the condition, she is maintaining what is called a private nuisance. You can sue to abate the nuisance, seeking an injunction (i.e., an order from the court prohibiting her from allowing the condition to persist).