Can you talk with her mother, see if/how you can help? I imagine if her parents know she's doing it to get attention they'll give her some more attention or would love to have you help out in some way. My stepmother use to take my nieces and nephews (her grandchildren) to the zoo on Saturday mornings so my stepsister could get some sleep. I know my stepson takes his 2 year old daughter to breakfast, just the two of them on Saturday morning so my daughter-in-law won't have so much to deal with (1 year old son) and can get some rest. Ask your niece what/where she'd like to go? Library? Local parks?