I think this person is lost in her own little Fi world. In Fi land, you stay connected to people through your imagination & can forget to contact them in reality. 6 months can feel like a few weeks in a relationship to me. It's hard for me to maintain friendships, even though I manage to stay emotionally connected to people despite lapses in contact.
Communication is key with an INFP. YES, we need to be hit over the head & told directly what you want. NO, we do not automatically know what we are supposed to do socially. I always feel like there was a day in school I missed, and that was the day everyone else was taught the social graces but me

. Thank goodness for my ISFJ mom who taught me about writing thank you cards & that sort of thing.
Quite honestly, I would not visit a sick friend, but I would probably email/call to see how they are doing. I would only visit if that friend expressly asked me to do so. Otherwise, I would feel like I was intruding. I can't say I would want to be bothered with visitors if I was laid up with a broken leg, and I tend to cast my feelings onto others.
Another thing, when I am not in the mood to socialize, I feel I am doing people a favor by staying away. I am just grouchy & moody & not good company, so I don't like to burden people with my presence. I don't see that as selfish....