Miley Cyrus, 28, is mourning the loss of her sweet dog Mary Jane. The 10-year-old pit bull mix sadly had to be put down after battling cancer for over a year. “Anyone who knows me & it doesn’t have to be well is aware that my best friend in the whole world is a rescued pit bull mix named Mary Jane,” Miley began her emotional tribute to her furry friend on Thursday, Jan. 7.