Demi Lovato [1] is singing Selena Gomez [2]'s praises after the 25-year-old actress and singer revealed to the world she underwent a kidney transplant over the Summer [3]. "I think that she is a very strong woman," Demi told People [4] on Friday evening after a performance in Los Angeles. "I'm very happy and proud of her," she gushed. Selena and Demi's friendship [5] had been on and off for a few years, with Demi revealing in a 2014 interview that she and Selena had grown apart [6]. The former Disney stars reunited in 2015 and shared an adorably silly selfie on Instagram [7] confirming their friendship was back on the mend. "Friends for years, #sameoldlove," Demi captioned the photo.