Hi and welcome to JA. I am Ray and will be the expert helping you today.
Here under California Civil Code Section 833, if the trunk of a tree stands wholly on the land of one landowner, that landowner owns the tree regardless of whether its roots, foliage, or branches have grown onto the land of another. However, if the trunk of a tree stands partly on the land of two adjoining landowner, then both landowners own the tree. (Civil Code Section 834).
Generally, the law considers shrubbery, foliage and branches that encroach onto the land of another a nuisance. The owner of the land encroached upon may abate the nuisance by trimming the overhanging foliage, branches and limbs so long as the owner acts reasonably so as not to seriously injure or kill the tree causing the nuisance. If a landowner cuts foliage that is not encroaching onto his property and does not have the permission of the tree's owner to trim, however, the person cutting the foliage may be liable to the adjoining landowner for up to triple the amount of the damage caused by the wrongful cutting. However, if the damage is accidental or based on a mistaken belief, damages may be limited in the court's discretion to double the value of the wrongful cutting. (Civil Code Section 3346).
A leading case is Metropolitan Water District v. Campus Crusade for Christ (2005), the California Court of Appeals ruled that the amount of damages to be awarded to a landowner whose trees were destroyed was the diminution in value of the property caused by the tree trimming, not the replacement cost of the trees. This case, however, is presently pending appeal before the California Supreme Court.
So you are allowed to trim to your bo9undary if the tree is on her side.You can with permission trim or take down beyond the boundary.The owner of the tree here unfortunately in California owns the tree.If it becomes dead or dying the owner may then have liability if it falls on your home or otherwise damages here.
You may be able to argue that you can trim to clear the easement and that seems reasonable to do so.But unless you can resolve it with the owner California does not hold the owner to trimming the encroachment unless it is dead or dying here.
Reference to these issues and more law..
You are allowed here to prune anything encroaching on your property or the easement as long as you do this reasonably.You can see if she would offer to split the bill here but if it is on your side that would be voluntary under the reference above.
I appreciate the chance to help you today.Please let me know if you have more follow up.Thanks again.