Babes.
At the end of the day, they are in a relationship.
If youre partner had all that stuff all over his chin, im sure you wouldnt treat them any differently because you love them and want to care for them when they are ill, and not treat them any differently because they would feel out of place.
The main thing you could do is just treat your friend as normal, she likes her boyfriend, and obviously cares for him if shes willing to sacrafice her health for him.
So just let them be, and treat them as you would normally
xxx