Hi and welcome. So sorry to hear about your granddaughter, so worrying for you all. It could possibly be emotional problems by the sound of it, but with a child the 1st thing to do is to get them checked out by their GP or DSN. I am not on a pump but I have a 6 year old GD with type 1 as well, but on injections.
Have you thought about her 'chatting to you' through drawings or paintings, or a diary she write or draw in, did it start when the she went onto the pump ? A great source of help should be her school, please make an appointment, with or without your son to see the Head teacher, or class teacher to find out how she is within the school, in the class, at break time, lunch times, as some children can be made to feel 'different' by their peers.
Please let us know how you get on and I wish you all the very best and for your GD to be happy.and to suffer anyone.
Best wishes RRB x