I am almost 100% sure that no 3rd party is around.
How did you determine this?
Have you examined the credit card bills for the past several months? Have you checked her cell phone records? Text messages? Email? Are the computer's email history/cookies constantly being erased? Does she still have large amounts of unaccounted-for time?
You may be nearly certain there's no 3rd party, but her behavior screams otherwise.
FC
