Infant Having Micro Or Partial Deletion Of Chromosome. Treatment?

My granddaughter is 11 months old. We have just been told she has a micro or partial deletion of chromosome 15 q11.2. She slept for the first 3 months of her life. It was extremely difficult to wake her up to eat. She is long for her age but she has microcephaly . However, her brain is not flat in the back. She is starting to say da da, ma ma, ni ni, ya ya and that is about it. She has muscle weakness but she can sit up. However, if she falls back she cannot get back to the seated position. She seems to have equal symptoms of prader willi and angelman syndromes. It will be several months before more testing can be done to determine which syndrome it is. Would you know of another way to tell for sure which syndrome she has?