Thats horrible! I cant thikn why they would do that but I dont know all thats happened anyway here. Seems no good excuse for it by the way thats their grand daughter. Sending the pics back is a direct spit in your face so to speak. They may not have attached a note or said anything biut that speaks volums, They do not want anythng to do not even a photo. Its cruel and they mean it as cruel but are they stubborn as it is cutting your own nose of to spite your face? deep hatred is seated there then. Well least you tried, do keep the package the send back as later on people who do things like that tend to forget about it when they want a relationship and walk back into your daughters life. You keep that reminded how they walked out so theres no confusion in the future when things are twisted about if that should happen.
It is hurtful to you as they wont have that set of grand parents I know but they dont sound nice poeple anyway. no lose.