[mslif]

When I read your initial post, I though that maybe she did not feel attractive anymore or that your marriage had become too routine. Then I read about the LBT and the thongs. As a woman (who has been married before) I found this behavior troublesome and I seriously think she is being unfaithful. If you are not the one enjoying her new accessories, somebody else is. Has she been working late? Has she gone to see friends more than usual? Stress at work is not a good enough excuse IMO.
I would not recommend buying her anything. Seeing a therapist would be a better idea or start following her around.