Jill's police ID number is 0823
She is known as the "Master Of Unlocking" and can use a lockpick to gain access to almost any locked door
In Resident Evil 2, if you search her desk (as Claire) you will find a framed photo of a young man "probably her boyfriend" thinks Claire. We never find out if this is infact her boyfriend or who the man in question is.
Jill Valentine was originally depicted as having long hair hidden under her beret, as noted by one of the game's alternate endings and official artwork. In later installments, she has short shoulder-length hair.
In the video game Dead Rising there is a restaurant called "Jill's Sandwiches", which is a parody of the infamous Barry Burton line from the first Resident Evil game: "You were almost a Jill Sandwich!". Also in the game if you look up the description of Jill's Sandwiches it states Jill is the master of sandwich making, an obvious parody of another infamous Barry line;
"Jill, here's a lockpick. It might be handy if you, the master of unlocking, take it with you."