this has happened a few times after new april 16 patch, not sure if it happen before patch.
I have noticed Lilith Valtore get confused and stay outside house after visit. I usually don't notice till after 10am+. my house is the crick cabana and she visits usually 8pm+. i invite her in, play chess, socialize for a bit, and she stays most the night while my sim is sleeping. then leaves toward morning. I will notice her usually in same spot, its close to where the sidewalk intersects from north / south and the sidewalk the runs in front of crick cabana house. shes on the north/south sidewalk a bit below the intersect. I do not think she is frozen because when its raining she will have umbrella also sim still doing slight movements they usually do while standing in one spot. if you approach with sim she will move a bit and fade to disappear. or run off screen.
I also noticed this only 1 time right in front of house toward front right corner of house on sidewalk with Summer Holiday (not vampire). she visit in morning and left shortly afterward, i noticed her pretty fast and walked toward her and she take a few steps and faded out. disappeared.
i have not modified the lots at all. except last night i added the tutorial house to the empty lot south of crick cabana same place of new tutorial placement. I also added 3 of the lot traits to crick cabana. Just skill increase lot traits. science lair, homey, and fast internet. i have made no other modification , except handy upgrade for appliances. upgraded to better bed (sold old and bought new one) and added a chess board 2 chairs in back bedroom.
