Best friend jealous! help!?

im pick my friend ashley to go on a trip to florida with me and when me and ashley post pics on Facebook abby will wonder why i didn't invite her but honestly me and ashley are closer than me and abby what do i tell abby when she see's hem and im definatley posting them so not is not an option. so the main Q is what do i tell her when she see? without being rude or mean.