What Causes Black Lips With Skinny Body?

Hi

My mum passed away a couple of weeks back, but I hadnt seen her in a couple of years for one re3ason and another, but when I got home and seen her before she passed, she had gotten very thin and her lips were black?

Is there any reason why her lips may have been black?

Her cause of death was her heart and her kidneys failing, which the doctors at the hospital were caused by her diabetes and a bad diet....but its the black lips before she died that concern me the most...are black lips medically a sign for anything???