The biggest thing you can do is help take care of the baby. They can rest, which is very important for getting over infections. Is she able to breastfeed? If she is nursing the baby, preparing snacks and easy food for her to grab and eat with one hand when she is alone would be great. She needs to get plenty of healthy food in. Make sure there are plenty of calories that are quality so that her body can fuel the production of milk without impeding the healing process. Some good options are yogurt with active cultures since she has been on antibiotics. Foods with healthy fats like avocados, nuts, fish, grass-fed beef, etc. These will boost her omega 3's which are vital for both mother and child right now. The iron in the beef will help her in the healing process and grass-fed beef is filled with healthy fat rather than saturated fat like regular red meat. Plenty of fruits and veggies. Cut up and prepare some for her as she doesn't have the energy.
Simple housework would help her a lot too. Just picking up, light vacuuming, organizing, doing the dishes, laundry etc will ease her burden and allow her more time with her feet up. The more rest and relaxation she gets, the faster she will heal!