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