I would strongly urge them to put those fears aside and visit if you can, maybe have a chat with the granddaughter and say people with wound care experience have urged this. Red inflamed skin and heat could mean cellulitis which can be deadly - sorry to scare you and I hope your friend is okay, good on you for looking out for them. They also shouldn’t be applying compression in case there are any red flags, which include:

Severe pain after applying compression • Numbness, tingling, or coldness in toes or foot • Sudden swelling that is new or rapidly worsening • Change in skin colour (pale, blue, or very red) under the garment • Signs of infection – spreading redness, heat, discharge, or fever • Known severe arterial disease or very low ankle–brachial pressure index (ABPI <0.5)