Hot compresses will definitely help. Also have her massage the area lightly and frequently. It is important that she keeps the milk flowing so she needs to either continue breastfeeding or at least pump the milk out.
Anti-inflammatories such as licorice root and yucca root can be used internally to help reduce the pain without affecting the milk.
Make sure she stays hydrated with water and gets plenty of rest and nutrition to keep up her immunity.
And yes, lecithin can help. Granules are the best. Recommended dose is 1 tablespoon 3 times daily with meals.
Have her limit or eliminate animal fats since these can aggravate the mastitis.