By the way, I came up with another cool idea: a chance to have one of the characters at the party (besides the host) already know the player. This wouldn't change much except to give an initial Friendship modifier, much as the Rebounding trait gives a boost to Romance.
Taking it further, if the character has LikesMen < 0, it probably means their bad experience was with the player, so that adds a negative factor. It could be possible to show up to a party with someone who already knows you and hates your guts.
There's also a counter that reduces the chance each time KnowsPlayer is true, so it's extremely unlikely for the player to show up to a party with exactly one degree of separation.