Your mother seems to be malnourished and due to old age this could be due to poor diet.
Kindly rule out renal failure
, hypoalbunemia, deep vein thrombosis
in her case as you have mentioned swelling and minor sores on her legs. Do get her cardiac status evaluated as well.
She has been on diuretics (lasix
) but it seems she is still in volume overload, so do take her to hospital and get her evaluated.