I can relate to what auntiehill describes, as it reminds me of a situation of my own...though I don't want to get too personally detailed, so forgive the pseudonyms.
When a very close family member (A) was dying several years back, another very close family member (B) was behaving in a very bizarre and attention-seeking manner. Now B had every reason to be very upset, and others (e.g., hospital staff) who didn't really know B seemed to take B's grieving at face value. But it was just very off...it was very much as if B was trying to take the attention away from A, the person who was on their deathbed. Very close family member C and I, in the midst of this, were very much on the same page throughout the ordeal...we were trying to come to terms with losing A, comforting and supporting each other...but neither of us could deal with B, whom we thought was just making a bad situation worse. When A passed and C and I were trying to have our last moment with A in the hospital room, I actually had to tell B to leave the room because B's behavior was so inappropriate and upsetting...plus, at that point, we'd been holding a lot in about B's behavior for several days.
When I read some about Munchausen syndrome after the fact, B's behavior seemed to check off every box...it was very much the equivalent of wearing the red dress at the funeral.
Regarding the condolences by Internet...I don't use social media myself, but I think that would be the rough equivalent of the card that gets passed around at the office when somebody loses a family member. I didn't know the deceased, and I don't know the bereaved socially, but it's the decent thing to do. And when I got that card myself, I was actually touched by it in the moment.