of the facility where she is living? One idea might be to explain the situation to the staff, especially if you have a pre-existing relationship with anyone there, and ask them if your packages are being received. I'm sure that does not violate any laws.
My heart goes out to you. This situation, as you've explained it, seems very sad and frustrating. (Maybe there is something I'm not grasping).
But the bigger problem, IMO (and I know nothing about the legalities, but I'm responding as a human being) is you should have a right to know why you are being denied contact and how her guardian was appointed. Was the guardian appointed by a judge? On what basis?
The real issue: Does your daughter want contact with you? What changed between the time you had good contact with her and the prohibition against contact? If it by your daughter's request, why did she make this decision? Or was it made on her behalf by her guardian or someone else? Was she convinced by a therapist or attorney that this was in her best interest? If so, why? Maybe she does want contact with you but was talked into a no contact order by someone else.
It would drive me crazy not understanding what had changed, or who made the changes. You are exercising great restraint and patience IMO.
The safest, most delicate way to go about this might be to hire a lawyer with some experience in family law. But I also don't see anything wrong with making inquiries by sending letters by registered mail, to the facility with questions you have about the things you are sending, and any other questions you have that do not invade her medical privacy. Then I would inquire with the Guardian and the system by which the Guardian was chosen. I just don't know how it is possible this happened without her parent being involved in some capacity--it's not your fault, but it just seems very wrong that the system did not involve you and keep you fully informed.
Anyway, I'm so sorry to read that you are in this current situation.
I hope you can get some answers. You absolutely deserve them!