What can I do?

So my 6 yr old daughter has been sneaking into her grandmothers room at night and stealing the phone and stay up all times of the night watching YouTube videos Monday night she stayed up till 6 am and ended up not going to school because she did not get not sleep last night she did it again and her grandma found her at 3am on the phone what can we do I her mother am not where she lives due to work so she stays with her what can we do I told her gma to ground her for a week no tv no phone no technology whatsoever what else can we do she does not listen I don't wanna spank because I feel it's not right but I'm this case I feel it's necessary. What can I do?

Please help i dont know what to do anymore this little girl is a big drama queen like I mean so dramatic