“I’m tireeeeeed… Cuz I Love Yooooouuu,” Lizzo captioned the three-minute video on Instagram while throwing in some Mean Girls vocab. “I saw @mileycyrus running and singing on a treadmill so I ran and sang on a treadmill. It was fetch. And F—ING HARD.”Cyrus reposted the video to her own Instagram Story, writing, “I love you more! When I’m…