Cal. Penal Code ยงยง 631, 632: It is a crime in California to intercept or eavesdrop upon any confidential communication, including a telephone call or wire communication, without the consent of all parties.
~~~~~~~~~
This means that both parties must know that the conversation is being recorded. What you can do is send her a letter (RRR) stating that as of such date, ALL conversations between you both will be recorded by you. If she contines to call and talk, she is giving 'implied' consent. If she says no, she will have to find some other way to communicate. You can also do this with taping conversations in person.
The thing is, if she refuses consent, the only other way you can communicate is by either atty., e-mail, or letter, which means it's STILL documented, or at least witnessed. Which is EXACTLY what you want.
Hope this helps..........