Swimming...low impact and a good cardiovascular workout.
Start by changing her diet. Take a fat burner. And consult with a physical therapist or a trainer.
There are great exercise equipment now that use the upper body and leave the lower body out of the picture. There are several types of bikes that use the arms to pedal rather than the legs, both indoor and outdoor. These are a great way to burn calories without engaging the hips. Swimming can also be helpful, but be cautious. Use a shallow pool and do movements like jumping or paddling using the arms rather than swimming laps and doing kicks. Strengthening moves are also important since more muscle means stronger joints and more calories burned when you get to doing the cardio. For strength moves, the pool is also a good way to go since it s low impact on the joints. Invest in some water fitness paddles, available through fitnesswholesale.com or other fitness equipment retailers. They are flat paddles with little holes in them that create great resistance under water. There are also some great water fitness classes available through gyms. Just make sure your friend tells the instructor about her hips so she can modify. Good luck!