Hi and welcoe to HCM.
I am sorry that you re confronting with such serious disease,but I am glad that your mum feels good.
It is always hard to predict every malignant disease.
Swollen legs can be caused by tumor
pressure on pelvic veins,and this isnt uncommon. But also you should look for heart and kidney
disease because both can cause swollen feet. Whatever it is she should lie with elevated leg,can put some pillow undernetah and do feet exercise. For the beginning blood pressure and echocardiography
and basic labs would be good to evaluate kidny and heart function,although those swelling arent gonna hurt her very much if this isnt exreme.
Wish you good health and good luck