The swelling
in the lower extremeties is a classic symptom, along with
the shortness
of breath.
The swelling can manifest itself from the bottom of her feet, up to, and including her lungs. If left unchecked, or unmedicated, she will become unable to take a breath, and it could kill her.
As far as stages go, I've been told I'm in stage 4 heart failure, but it doesn't mean I'm in CHF, it means that my EF is 15-20%.