I don't have an sure fire address, however based on a little research on
http://www.fanmail.biz
You can try (which she has sent out mail from in 2005 and who knows she may still be using it)
Mailbox planet inc
530 south lake ave.
pasadena CA 91101
USA
Chris Masterson says FOX still forwards him fanmail, how reliable this method is I don't know, but...
Malcolm In The Middle
4024 Radford Ave.
Studio City, CA 91604
USA
http://www.fanmail.biz has this address as most uptodate, you could allways ring them and ask!
Jane Kaczmarek
Greenlight Management & Production
315 South Beverly Drive
Suite 300
Beverly Hills, CA 90212-4312
USA
Phone: (310) 201-5077
Would be awesome if you did establish a correct address and post your results
Send a Self Address Envelope or a more likely response.