I live in California where the law states that a landlord must return a security deposit within 21 days of the tenant vacating the property.

Are there penalties if the landlord does not return it in the specified time frame and if so what are they?

And, the landlord never asked for my new address to return the deposit but she does know how to contact me and if she sends it to the rental address it will be forwarded. Could her failure to return the deposit be construed as my fault for not giving her my address?

I assumed she never asked because she had no intention of ever returning the money. (by the way it is $5000)

If the landlord does not return the deposit within the time frame, or does not provide you with a written, detailed accounting of how the deposit was used within that time frame, then the landlord is not entitled to retain any of the deposit.

If you file a lawsuit then a judge can award you up to two times the amount that was wrongfully withheld.

If you did not provide a forwarding address to the landlord then they are required to send it to your last known address.

You can read more about California law concerning security deposits at Landlord/Tenant Book Index - California Department of Consumer Affairs (http://www.dca.ca.gov/publications/landlordbook/index.shtml)