I've been giving this some thought, Woodland... another way to look at it, perhaps... if there had been other threats or she had been targeted in some way previously, she apparently had not shared those concerns with LE either (as far as we know)... so if she mentally linked the mailbox vandalism to some perceived threat, it may have been just one more thing she was either afraid to report or she decided to deal with on her own. Perhaps because she had an inkling as to who her 'stalker' might be, and thought she could handle it herself? Which may have led to her setting up a scenario to catch someone who expected her to be away from the house having coffee with her group on Wednesday (as suggested by previous posters)?
I can see AG may have felt threatened and decided to take care of it herself - she apparently mentioned to a neighbour she did not feel safe to go outside at night without her dogs.
Unfortunately, two things make that fall part for me where AG is concerned. AG did go outside without her dogs on her last night. Prior to that, she is reported to have gone traipsing off to a hardware store to steal a part that belonged to her, following vandalism to her property, risking being caught on a security camera and stopped before she got back into the vehicle she arrived in. The choices make no sense to me from a clever person, or a person that may have felt some sort of threat.