|I'm sorry that you are going through so much despair for the loss of your dear mother...She obviously is very happy and healthy once again now. I do understand as I felt a lot of the same when my mother passed.
Yes, your niece did indeed have a Dream Visit. There is no doubt. A Dream Visit is very vivid, happy, and the person keeps a clear long time memory of it.
The numbers you say your brother sees are also a sign/ADC from your mother too....Triple or quadruple numbers that are the same are often referred to as "Angel Numbers". (My husband and I both get them. This morning it was - 10:10)
Don't be hesitant to continue talking to your mother, Joe. Talk to her as you fall asleep, as you've been doing. She does hear you!