shit is messed up mane, sometimes hard to realize and comprehend
to be honest it sounds like your GF noticed it alot more than you, did your father have a good relationship with her? it could be coincidence, it could be a blessing for both of you...I didnt really see a face, but if it means something to your gf, it means shes aware and caring and lookin out mane, if anything, its a great sign...
to be honest, if both of you beleive it was him, whos to tell you it wasnt, life goes on, the soul is a very real thing, have you looked at any other pics of you with a shadow?