We are "jointly and severally liable for rent in a Month to month rental agreement.
One of us wants to move. What are the legal rights of the person moving to get her rent back in California?

None, you must give a 30 day notice to the landlord. No notice and you continue to be obligated month to month, even if you have moved out. If you paid for September you can't get any money from roommate or LL. If you have not given notice yet you may also owe for October.

None, you must give a 30 day notice to the landlord. No notice and you continue to be obligated month to month, even if you have moved out. If you paid for September you can't get any money from roomate or LL. If you have not given notice yet you may also owe for October.

I've given the 30 day notice, but the landlord says I must get the deposit from the other tenet.. can she do that? If I paid the deposit isn't she obligated to return it to me?

Nope, LL get a full deposit if anyone is living there. If your roommate is the one that stays she needs to give you your half since she will get the full deposit when she leaves. Sounds funky but that's how it works so the LL doesn't get stuck with having only half of a deposit on a full rental unit.