She's been sitting for months but she just started rocking back and forth. She starts in a sitting position and leans to one side, plants both hands and starts rocking. She can inch her way to whatever it is she is trying to get.

She will also roll back and forth from belly to back and inch backwards to get to toys.

Update 7/16: she now scoots on her bottom to get to where she needs to go. Same sideways lean, then scoot. It's getting faster!