yeah, i'm not sure it's about making her happy (thundershirt's not a happy pill), it's just supposed to help her anxiety and to keep her calm down in stressful circumstances.
trying to recall.. doesn't Maggie get anxious around other people and dogs she doesn't know? and maybe storms? that's what to measure the intervention with, not if she's happy with it (ie. my dog may not like his pill or antibiotic, but it helps him with his infection...). it just has to help her with her anxiety and nervousness, that's the measure of whether it's working.
my 2 cents-- Worm
ps. Maggie, a burrito!! so cute. and you are making me awfully hungry....