I am so sorry for your pain. The adoptive family should honor you with what they promised. I don't get when adoptive parents will send only one or two pictures..

That is an insult to the birthparents. I am so worried that I don't send enough but I send alot. I would be honest with the adoptive family. You don't need to be going through any more of this. If you don't tell them, things will get worse for you. Just be honest and open with them. Do you get to talk on the phone or email them? Your daughter is 4 now, things can still change for the better for everyone involved. Just let them know that you are not trying to take their places as parent. Maybe write down some things you will like to say to them. If they are caring at all, they will want to make some changes for you...
One more thing. Some adoptive families are threatened by birthfamilies for some dang reason. I think they watch too many dumb movies on Lifetime..

Please know that I will keep you in my prayers that things will change for you...
Take care and PM me if you need to talk to an Adoptive mom.. Thank God I keep my promises to my kids birthmom's...
PS..Your daughter's parents should be forever grateful to you that you allowed them to parent your daughter..