Legal Question in Landlord & Tenant Law in California

Logically, an e-mail should be the same as something in writing, but all the code sections werre written using the term "wriltten". She probably has done enough but I would follow up with a letter [copy e-mailed] stating that the end of 1/15/2011 is the longest she can stay and all of her possessions and heself must be out by the end of the day and the keys eturned to your sister [I am assuming she was there less than one year]. Saying "as soon as I can" is not acceptable because that is not a specific date. Also tell her that if she leaves before 1/15 she must give 24 hours notice and since your sister has to then clean the place up and advertise it for rent, wilthout knowing for sure a specific date she can not do that and at least some of the days before 1/15 will be unproductive so rent will be charged to her. Be sure to give the 21 day wriltten statement of what security deposit amount retained and why.