The Coreg, in the right
dose, should help her heart beat more efficiently and stronger, helping to pump the fluid from her lungs, and the lasix would help clear the fluid from her system.
Something else that I have had in the past, for CHF, is albuterol. While most doctors don't like to use it with heart patients, it works real well for clearing the lungs. Albuterol took me from 100% whiteout, to completely clear lungs in about 20 minutes, and they stayed clear for several days.