1984 Oct 6 married Ryan Arthur Eastwood of Ferndale, Officiated by Ronald Knutson, Witnessed by Brad Oxford and Kim Cook. nwwtcmcv84b_419 https://www.digitalarchives.wa.gov/Record/View/4788D44E9B619803C82BBD70DB3D679B
Dec. 20, 1988, a Whatcom County divorce decree was issued. CB7E10AC-AB18-4684-AEA9-4667A3430222 https://www.digitalarchives.wa.gov/Record/View/5F95FC02963E9B098A57E58E2A30C1C5.

[BTW: Cindy A Rustand was born in 1961, the older sister of Sandy, not an alias as suggested elsewhere. To rectify that misinformation and provide more details about the interconnections of these sisters:
December 13, 1980, at age 19 Cindy Rustand married 20 year old Bruce Lahtonen (FHS Class of 1978) of Seattle in Whatcom County, officiated by Methodist minister Graham Hutchins, witnessed by Tammy O'Brine and John Rideout - his 1980 signature witnessing Cindy Rustand's marriage seems to match that of his 1989 marriage to her younger sister Sandy Rustand.
nwwtcmcv80b_628 https://www.digitalarchives.wa.gov/Record/View/78696AC1DD3893D36E2B59C6740FEB33
February 29, 1984, a Yakima County divorce decree was issued between Cindy A Rustand (around age 22) and Bruce A. LAHTONEN. 6EAF6F69-F3E9-4B88-B5A9-235DFEE22ED1
https://www.digitalarchives.wa.gov/Record/View/FEE3BDE1A815F9456CA773E952EFC189]

A marriage of Nov. 17, 1984 was recorded between Cindy A Rustand age 23 and Timothy A Zawicki age 21 of Lynden, Officiated by William Gunter of Snohomish, witnessed by Dan and Cris Thompson (Tim's sister). nwwtcmcv84b_526 https://www.digitalarchives.wa.gov/Record/View/6889298EE7ADD7C3B3E42362E7564EFE
After Sandy's disappearance, on Nov. 11/17/2006, a Whatcom County divorce decree was issued for Cindy and Tim: 6BCBCDBA-FF37-443F-A6DA-93E81B534E13
https://www.digitalarchives.wa.gov/Record/View/0590F2FDE6AEEA0A7D151A050E735FFD ]

1989 Dec 2 at age 24, Sandy Rustand married 30 year old John Clark Rideout of Blaine, Officiated by Floyd Iverson, and Witnessed by Karl Bocek and Crystal Lasher; nwwtcmcv89b_626 from https://www.digitalarchives.wa.gov/Record/View/EDC6767D1FAA6BA9F589FAC8429BB997

Sandy's last known physical address was in Ferndale. A sighting was reported April 24, 2006 in Bellingham. At age 41, she was reported as a missing person by the Whatcom County Sheriff’s Office. The National Missing Person Directory listed her Appearance as:
Hair: Brown; Head Hair: Past shoulder length, straight
Eye: Brown
Piercings: Pierced ears
Height: 64.0
Weight: 115.0 Other Distinctive: 'Bloaty' from drugs and alcohol
http://www.missingin.org/reg3986/sandy_l__rideout.htm
Though last seen in Bellingham, it is believed she frequented the Seattle are around that time. She did at one time live in Seattle.
Up until March of 2008 it seems she was still receiving mail at a downtown Seattle address. More correctly someone was collecting unemployment benefits for her during that time (2008, March 27 King County Superior Court case 89-9-10279-9. https://i0.wp.com/snocoreporter.com/wp-content/uploads/2015/12/Washington-Courts-Search-Case-Records-2015-12-06-13-55-00.png

Thanks to contributor Lyn Cole for this 2015 update: Remains found on privately-owned timber land, about 5 miles west of SR 2 between Gold Bar and Index, Skagit Valley, Washington, 2015, on November, 25th, by loggers. This was about 100 miles south of Ferndale. IDENTIFIED: The skeletal remains were identified to Sandy in less than a week, Friday, December 4th, 2015, by the Snohomish County Medical Examiner's Office. The cause and manner of death are undetermined.
https://snohomishcountywa.gov/DocumentCenter/View/34891